PXAG30KBBD ,XA-G30; XA 16-bit microcontroller family 512 B RAM, watchdog, 2 UARTsBLOCK DIAGRAM . . . . . . . 3PIN DESCRIPTIONS . . . . . 4SPECIAL FUNCTION REGIS ..
PXAG30KBBD ,XA-G30; XA 16-bit microcontroller family 512 B RAM, watchdog, 2 UARTsINTEGRATED CIRCUITSXA-G30XA 16-bit microcontroller family512 B RAM, watchdog, 2 UARTsProduct data 2 ..
PXAG30KBBD ,XA-G30; XA 16-bit microcontroller family 512 B RAM, watchdog, 2 UARTs
PXAG30KFA ,XA-G30; XA 16-bit microcontroller family 512 B RAM, watchdog, 2 UARTsapplications.• Low power operation, which is intrinsic to the XA architecture,includes power-down a ..
PXAG30KFBD ,XA-G30; XA 16-bit microcontroller family 512 B RAM, watchdog, 2 UARTsELECTRICAL CHARACTERISTICS (VDD = 2.7 V TO 4.5 V) . . . . . . . 23REVISION HISTORY . ..
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R5101G001A , Microprocessor power management with Watchdog Timer
R5220D032A , PWM Step-down DC/DC Converter with switch function
R5321D003A-TR , CMOS 2ch-LDOs for RF Unit
R5321D008A-TR , CMOS 2ch-LDOs for RF Unit
PXAG30KBA-PXAG30KBBD-PXAG30KFA-PXAG30KFBD
XA-G30; XA 16-bit microcontroller family 512 B RAM, watchdog, 2 UARTs
Product data
Replaces datasheet XA-G3 of 2001 Jun 25
2002 Mar 25
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
FAMILY DESCRIPTION 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPECIFIC FEATURES OF THE XA-G30 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ORDERING INFORMATION 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PIN CONFIGURATIONS 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44-Pin PLCC Package 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44-Pin LQFP Package 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LOGIC SYMBOL 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
BLOCK DIAGRAM 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PIN DESCRIPTIONS 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SPECIAL FUNCTION REGISTERS 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
XA-G30 TIMER/COUNTERS 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timer 0 and Timer 1 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
New Enhanced Mode 0 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mode 1 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mode 2 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mode 3 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
New Timer-Overflow Toggle Output 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Timer T2 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Capture Mode 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Auto-Reload Mode (Up or Down Counter) 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Baud Rate Generator Mode 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Programmable Clock-Out 11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
WATCHDOG TIMER 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Watchdog Function 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Watchdog Control Register (WDCON) 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Watchdog Detailed Operation 13. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
WDCON Register Bit Definitions 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
UARTS 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Serial Port Control Register 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TI Flag 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9-bit Mode 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bypassing Double Buffering 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Note Regarding Older XA-G30 Devices 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CLOCKING SCHEME/BAUD RATE GENERATION 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Using Timer 2 to Generate Baud Rates 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Prescaler Select for Timer Clock (TCLK) 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
UART INTERRUPT SCHEME 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Error Handling, Status Flags and Break Detect 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Multiprocessor Communications 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Automatic Address Recognition 17. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O PORT OUTPUT CONFIGURATION 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EXTERNAL BUS 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RESET 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
RESET OPTIONS 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
POWER REDUCTION MODES 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INTERRUPTS 20. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ABSOLUTE MAXIMUM RATINGS 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DC ELECTRICAL CHARACTERISTICS 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
AC ELECTRICAL CHARACTERISTICS 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
AC ELECTRICAL CHARACTERISTICS (VDD = 4.5 V TO 5.5 V) 22. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
AC ELECTRICAL CHARACTERISTICS (VDD = 2.7 V TO 4.5 V) 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
FAMILY DESCRIPTIONThe Philips Semiconductors XA (eXtended Architecture) family of
16-bit single-chip microcontrollers is powerful enough to easily
handle the requirements of high performance embedded
applications, yet inexpensive enough to compete in the market for
high-volume, low-cost applications.
The XA family provides an upward compatibility path for 80C51
users who need higher performance and 64k or more of program
memory. Existing 80C51 code can also easily be translated to run
on XA microcontrollers.
The performance of the XA architecture supports the
comprehensive bit-oriented operations of the 80C51 while
incorporating support for multi-tasking operating systems and
high-level languages such as C. The speed of the XA architecture,
at 10 to 100 times that of the 80C51, gives designers an easy path
to truly high performance embedded control.
The XA architecture supports: Upward compatibility with the 80C51 architecture 16-bit fully static CPU with a 24-bit program and data address
range Eight 16-bit CPU registers each capable of performing all
arithmetic and logic operations as well as acting as memory
pointers. Operations may also be performed directly to memory. Both 8-bit and 16-bit CPU registers, each capable of performing
all arithmetic and logic operations. An enhanced instruction set that includes bit intensive logic
operations and fast signed or unsigned 16 × 16 multiply and
32 / 16 divide Instruction set tailored for high level language support Multi-tasking and real-time executives that include up to 32
vectored interrupts, 16 software traps, segmented data memory,
and banked registers to support context switching Low power operation, which is intrinsic to the XA architecture,
includes power-down and idle modes.
More detailed information on the core is available in the XA User
Guide.
SPECIFIC FEATURES OF THE XA-G30 20-bit address range, 1 megabyte each program and data space.
(Note that the XA architecture supports up to 24 bit addresses.) 2.7 V to 5.5 V operation 512 bytes of on-chip data RAM Three counter/timers with enhanced features
(equivalent to 80C51 T0, T1, and T2) Watchdog timer Two enhanced UARTs Four 8-bit I/O ports with 4 programmable output configurations 44-pin PLCC and 44-pin LQFP packages
ORDERING INFORMATION
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
PIN CONFIGURATIONS
44-Pin PLCC Package
44-Pin LQFP Package
LOGIC SYMBOL
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
BLOCK DIAGRAM
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
PIN DESCRIPTIONS
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
SPECIAL FUNCTION REGISTERS
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
NOTES: SFRs are bit addressable. At reset, the BCR register is loaded with the binary value 0000 0a11, where “a” is the value on the BUSW pin. This defaults the address bus
size to 20 bits since the XA-G30 has only 20 address lines. SFR is loaded from the reset vector. All bits except F1, F0, and P are loaded from the reset vector. Those bits are all 0. Unimplemented bits in SFRs are X (unknown) at all times. Ones should not be written to these bits since they may be used for other
purposes in future XA derivatives. The reset value shown for these bits is 0. Port configurations default to quasi-bidirectional when the XA begins execution from internal code memory after reset, based on the
condition found on the EA pin. Thus all PnCFGA registers will contain FF and PnCFGB registers will contain 00. When the XA begins
execution using external code memory, the default configuration for pins that are associated with the external bus will be push-pull. The
PnCFGA and PnCFGB register contents will reflect this difference. The WDCON reset value is E6 for a Watchdog reset, E4 for all other reset causes. The XA-G30 implements an 8-bit SFR bus, as stated in Chapter 8 of the XA User Guide. All SFR accesses must be 8-bit operations. Attempts
to write 16 bits to an SFR will actually write only the lower 8 bits. Sixteen bit SFR reads will return undefined data in the upper byte.
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
XA-G30 TIMER/COUNTERSThe XA has two standard 16-bit enhanced Timer/Counters: Timer 0
and Timer 1. Additionally, it has a third 16-bit Up/Down
timer/counter, T2. A central timing generator in the XA core provides
the time-base for all XA Timers and Counters. The timer/event
counters can perform the following functions: Measure time intervals and pulse duration Count external events Generate interrupt requests Generate PWM or timed output waveforms
All of the timer/counters (Timer 0, Timer 1 and Timer 2) can be
independently programmed to operate either as timers or event
counters via the C/T bit in the TnCON register. All timers count up
unless otherwise stated. These timers may be dynamically read
during program execution.
The base clock rate of all of the timers is user programmable. This
applies to timers T0, T1, and T2 when running in timer mode (as
opposed to counter mode), and the watchdog timer. The clock
driving the timers is called TCLK and is determined by the setting of
two bits (PT1, PT0) in the System Configuration Register (SCR).
The frequency of TCLK may be selected to be the oscillator input
divided by 4 (Osc/4), the oscillator input divided by 16 (Osc/16), or
the oscillator input divided by 64 (Osc/64). This gives a range of
possibilities for the XA timer functions, including baud rate
generation, Timer 2 capture. Note that this single rate setting applies
to all of the timers.
When timers T0, T1, or T2 are used in the counter mode, the
register will increment whenever a falling edge (high to low
transition) is detected on the external input pin corresponding to the
timer clock. These inputs are sampled once every 2 oscillator
cycles, so it can take as many as 4 oscillator cycles to detect a
transition. Thus the maximum count rate that can be supported is
Osc/4. The duty cycle of the timer clock inputs is not important, but
any high or low state on the timer clock input pins must be present
for 2 oscillator cycles before it is guaranteed to be “seen” by the
timer logic.
Timer 0 and Timer 1The “Timer” or “Counter” function is selected by control bits C/T in
the special function register TMOD. These two Timer/Counters have
four operating modes, which are selected by bit-pairs (M1, M0) in
the TMOD register. Timer modes 1, 2, and 3 in XA are kept identical
to the 80C51 timer modes for code compatibility. Only the mode 0 is
replaced in the XA by a more powerful 16-bit auto-reload mode. This
will give the XA timers a much larger range when used as time
bases.
The recommended M1, M0 settings for the different modes are
shown in Figure 2.
Figure 1. System Configuration Register (SCR)
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
New Enhanced Mode 0For timers T0 or T1 the 13-bit count mode on the 80C51 (current
Mode 0) has been replaced in the XA with a 16-bit auto-reload
mode. Four additional 8-bit data registers (two per timer: RTHn and
RTLn) are created to hold the auto-reload values. In this mode, the
TH overflow will set the TF flag in the TCON register and cause both
the TL and TH counters to be loaded from the RTL and RTH
registers respectively.
These new SFRs will also be used to hold the TL reload data in the
8-bit auto-reload mode (Mode 2) instead of TH.
The overflow rate for Timer 0 or Timer 1 in Mode 0 may be
calculated as follows:
Timer_Rate = Osc / (N * (65536 – Timer_Reload_Value))
where N = the TCLK prescaler value: 4 (default), 16, or 64.
Mode 1Mode 1 is the 16-bit non-auto reload mode.
Mode 2Mode 2 configures the Timer register as an 8-bit Counter (TLn) with
automatic reload. Overflow from TLn not only sets TFn, but also
reloads TLn with the contents of RTLn, which is preset by software.
The reload leaves THn unchanged.
Mode 2 operation is the same for Timer/Counter 0.
The overflow rate for Timer 0 or Timer 1 in Mode 2 may be
calculated as follows:
Timer_Rate = Osc / (N * (256 – Timer_Reload_Value))
where N = the TCLK prescaler value: 4, 16, or 64.
Mode 3Timer 1 in Mode 3 simply holds its count. The effect is the same as
setting TR1 = 0.
Timer 0 in Mode 3 establishes TL0 and TH0 as two separate
counters. TL0 uses the Timer 0 control bits: C/T, GATE, TR0, INT0,
and TF0. TH0 is locked into a timer function and takes over the use
of TR1 and TF1 from Timer 1. Thus, TH0 now controls the “Timer 1”
interrupt.
Mode 3 is provided for applications requiring an extra 8-bit timer.
When Timer 0 is in Mode 3, Timer 1 can be turned on and off by
switching it out of and into its own Mode 3, or can still be used by
the serial port as a baud rate generator, or in fact, in any application
not requiring an interrupt.
Figure 3. Timer/Counter Control (TCON) Register
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
Figure 4. Timer/Counter 2 Control (T2CON) Register
New Timer-Overflow Toggle OutputIn the XA, the timer module now has two outputs, which toggle on
overflow from the individual timers. The same device pins that are
used for the T0 and T1 count inputs are also used for the new
overflow outputs. An SFR bit (TnOE in the TSTAT register) is
associated with each counter and indicates whether Port-SFR data
or the overflow signal is output to the pin. These outputs could be
used in applications for generating variable duty cycle PWM outputs
(changing the auto-reload register values). Also variable frequency
(Osc/8 to Osc/8,388,608) outputs could be achieved by adjusting
the prescaler along with the auto-reload register values. With a
30.0MHz oscillator, this range would be 3.58Hz to 3.75MHz.
Timer T2Timer 2 in the XA is a 16-bit Timer/Counter which can operate as
either a timer or as an event counter. This is selected by C/T2 in the
special function register T2CON. Upon timer T2 overflow/underflow,
the TF2 flag is set, which may be used to generate an interrupt. It
can be operated in one of three operating modes: auto-reload (up or
down counting), capture, or as the baud rate generator (for either or
both UARTs via SFRs T2MOD and T2CON). These modes are
shown in Table 1.
Capture ModeIn the capture mode there are two options which are selected by bit
EXEN2 in T2CON. If EXEN2 = 0, then timer 2 is a 16-bit timer or
counter, which upon overflowing sets bit TF2, the timer 2 overflow
bit. This will cause an interrupt when the timer 2 interrupt is enabled.
If EXEN2 = 1, then Timer 2 still does the above, but with the added
feature that a 1-to-0 transition at external input T2EX causes the
current value in the Timer 2 registers, TL2 and TH2, to be captured
into registers RCAP2L and RCAP2H, respectively. In addition, the
transition at T2EX causes bit EXF2 in T2CON to be set. This will
Auto-Reload Mode (Up or Down Counter)In the auto-reload mode, the timer registers are loaded with the
16-bit value in T2CAPH and T2CAPL when the count overflows.
T2CAPH and T2CAPL are initialized by software. If the EXEN2 bit in
T2CON is set, the timer registers will also be reloaded and the EXF2
flag set when a 1-to-0 transition occurs at input T2EX. The
auto-reload mode is shown in Figure 8.
In this mode, Timer 2 can be configured to count up or down. This is
done by setting or clearing the bit DCEN (Down Counter Enable) in
the T2MOD special function register (see Table 1). The T2EX pin
then controls the count direction. When T2EX is high, the count is in
the up direction, when T2EX is low, the count is in the down
direction.
Figure 8 shows Timer 2, which will count up automatically, since
DCEN = 0. In this mode there are two options selected by bit
EXEN2 in the T2CON register. If EXEN2 = 0, then Timer 2 counts
up to FFFFH and sets the TF2 (Overflow Flag) bit upon overflow.
This causes the Timer 2 registers to be reloaded with the 16-bit
value in T2CAPL and T2CAPH, whose values are preset by
software. If EXEN2 = 1, a 16-bit reload can be triggered either by an
overflow or by a 1-to-0 transition at input T2EX. This transition also
sets the EXF2 bit. If enabled, either TF2 or EXF2 bit can generate
the Timer 2 interrupt.
In Figure 9, the DCEN = 1; this enables the Timer 2 to count up or
down. In this mode, the logic level of T2EX pin controls the direction
of count. When a logic ‘1’ is applied at pin T2EX, the Timer 2 will
count up. The Timer 2 will overflow at FFFFH and set the TF2 flag,
which can then generate an interrupt if enabled. This timer overflow,
also causes the 16-bit value in T2CAPL and T2CAPH to be
reloaded into the timer registers TL2 and TH2, respectively.
A logic ‘0’ at pin T2EX causes Timer 2 to count down. When
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
timer register is loaded with FFFF hex. The underflow also sets the
TF2 flag, which can generate an interrupt if enabled.
The external flag EXF2 toggles when Timer 2 underflows or
overflows. This EXF2 bit can be used as a 17th bit of resolution, if
needed. the EXF2 flag does not generate an interrupt in this mode.
As the baud rate generator, timer T2 is incremented by TCLK.
Baud Rate Generator ModeBy setting the TCLKn and/or RCLKn in T2CON or T2MOD, the
Timer 2 can be chosen as the baud rate generator for either or both
UARTs. The baud rates for transmit and receive can be
simultaneously different.
Programmable Clock-OutA 50% duty cycle clock can be programmed to come out on P1.6.
This pin, besides being a regular I/O pin, has two alternate
functions. It can be programmed (1) to input the external clock for
Timer/Counter 2 or (2) to output a 50% duty cycle clock ranging from
3.58Hz to 3.75MHz at a 30MHz operating frequency.
To configure the Timer/Counter 2 as a clock generator, bit C/T2 (in
T2CON) must be cleared and bit T20E in T2MOD must be set. Bit
TR2 (T2CON.2) also must be set to start the timer.
The Clock-Out frequency depends on the oscillator frequency and
the reload value of Timer 2 capture registers (TCAP2H, TCAP2L) as
shown in this equation:
TCLK �(65536� TCAP2H, TCAP2L)
In the Clock-Out mode Timer 2 roll-overs will not generate an
interrupt. This is similar to when it is used as a baud-rate generator.
It is possible to use Timer 2 as a baud-rate generator and a clock
generator simultaneously. Note, however, that the baud-rate will be
1/8 of the Clock-Out frequency.
Table 1. Timer 2 Operating Modes
Figure 5. Timer 0 And 1 Extended Status (TSTAT)
Figure 6. Timer 2 Mode Control (T2MOD)
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
Figure 7. Timer 2 in Capture Mode
Figure 8. Timer 2 in Auto-Reload Mode (DCEN = 0)
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
WATCHDOG TIMERThe watchdog timer subsystem protects the system from incorrect
code execution by causing a system reset when the watchdog timer
underflows as a result of a failure of software to feed the timer prior
to the timer reaching its terminal count. It is important to note that
the watchdog timer is running after any type of reset and must be
turned off by user software if the application does not use the
watchdog function.
Watchdog FunctionThe watchdog consists of a programmable prescaler and the main
timer. The prescaler derives its clock from the TCLK source that also
drives timers 0, 1, and 2. The watchdog timer subsystem consists of
a programmable 13-bit prescaler, and an 8-bit main timer. The main
timer is clocked (decremented) by a tap taken from one of the top
8-bits of the prescaler as shown in Figure 10. The clock source for
the prescaler is the same as TCLK (same as the clock source for
the timers). Thus the main counter can be clocked as often as once
every 32 TCLKs (see Table 2). The watchdog generates an
underflow signal (and is autoloaded from WDL) when the watchdog
is at count 0 and the clock to decrement the watchdog occurs. The
watchdog is 8 bits wide and the autoload value can range from 0 to
FFH. (The autoload value of 0 is permissible since the prescaler is
cleared upon autoload).
This leads to the following user design equations. Definitions: tOSC
is the oscillator period, N is the selected prescaler tap value, W is
the main counter autoload value, P is the prescaler value from
Table 2, tMIN is the minimum watchdog time-out value (when the
autoload value is 0), tMAX is the maximum time-out value (when the
autoload value is FFH), tD is the design time-out value.
tMIN = tOSC × 4 × 32 (W = 0, N = 4)
tMAX = tOSC × 64 × 4096 × 256 (W = 255, N = 64)
tD = tOSC × N × P × (W + 1)
The watchdog timer is not directly loadable by the user. Instead, the
value to be loaded into the main timer is held in an autoload register.
In order to cause the main timer to be loaded with the appropriate
value, a special sequence of software action must take place. This
operation is referred to as feeding the watchdog timer.
To feed the watchdog, two instructions must be sequentially
executed successfully. No intervening SFR accesses are allowed,
so interrupts should be disabled before feeding the watchdog. The
instructions should move A5H to the WFEED1 register and then
5AH to the WFEED2 register. If WFEED1 is correctly loaded and
WFEED2 is not correctly loaded, then an immediate watchdog reset
will occur. The program sequence to feed the watchdog timer or
cause new WDCON settings to take effect is as follows:
clr ea ; disable global interrupts.
mov.b wfeed1,#A5h ; do watchdog feed part 1
mov.b wfeed2,#5Ah ; do watchdog feed part 2
setb ea ; re-enable global interrupts.
This sequence assumes that the XA interrupt system is enabled and
there is a possibility of an interrupt request occurring during the feed
sequence. If an interrupt was allowed to be serviced and the service
routine contained any SFR access, it would trigger a watchdog
reset. If it is known that no interrupt could occur during the feed
sequence, the instructions to disable and re-enable interrupts may
The software must be written so that a feed operation takes place
every tD seconds from the last feed operation. Some tradeoffs may
need to be made. It is not advisable to include feed operations in
minor loops or in subroutines unless the feed operation is a specific
subroutine.
To turn the watchdog timer completely off, the following code
sequence should be used:
mov.b wdcon,#0 ; set WD control register to clear WDRUN.
mov.b wfeed1,#A5h ; do watchdog feed part 1
mov.b wfeed2,#5Ah ; do watchdog feed part 2
This sequence assumes that the watchdog timer is being turned off
at the beginning of initialization code and that the XA interrupt
system has not yet been enabled. If the watchdog timer is to be
turned off at a point when interrupts may be enabled, instructions to
disable and re-enable interrupts should be added to this sequence.
Watchdog Control Register (WDCON)The reset values of the WDCON and WDL registers will be such that
the watchdog timer has a timeout period of 4 × 4096 × tOSC and the
watchdog is running. WDCON can be written by software but the
changes only take effect after executing a valid watchdog feed
sequence.
Table 2. Prescaler Select Values in WDCON
Watchdog Detailed OperationWhen external RESET is applied, the following takes place: Watchdog run control bit set to ON (1). Autoload register WDL set to 00 (min. count). Watchdog time-out flag cleared. Prescaler is cleared. Prescaler tap set to the highest divide. Autoload takes place.
When coming out of a hardware reset, the software should load the
autoload register and then feed the watchdog (cause an autoload).
If the watchdog is running and happens to underflow at the time the
external RESET is applied, the watchdog time-out flag will be
cleared.
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
Figure 10. Watchdog Timer in XA-G30When the watchdog underflows, the following action takes place
(see Figure 10): Autoload takes place.• Watchdog time-out flag is set Watchdog run bit unchanged.• Autoload (WDL) register unchanged.• Prescaler tap unchanged. All other device action same as external reset.
Note that if the watchdog underflows, the program counter will be
loaded from the reset vector as in the case of an internal reset. The
watchdog time-out flag can be examined to determine if the
watchdog has caused the reset condition. The watchdog time-out
flag bit can be cleared by software.
WDCON Register Bit DefinitionsWDCON.7 PRE2 Prescaler Select 2, reset to 1
WDCON.6 PRE1 Prescaler Select 1, reset to 1
WDCON.5 PRE0 Prescaler Select 0, reset to 1
WDCON.4 —
WDCON.3 —
WDCON.2 WDRUN Watchdog Run Control bit, reset to 1
WDCON.1 WDTOF Timeout flag
WDCON.0 —
UARTsThe XA-G30 includes 2 UART ports that are compatible with the
enhanced UART used on the 8xC51FB. Baud rate selection is
somewhat different due to the clocking scheme used for the XA
timers.
Some other enhancements have been made to UART operation.
The first is that there are separate interrupt vectors for each UART’s
transmit and receive functions. The UART transmitter has been
double buffered, allowing packed transmission of data with no gaps
between bytes and less critical interrupt service routine timing. A
break detect function has been added to the UART. This operates
independently of the UART itself and provides a start-of-break status
bit that the program may test. Finally, an Overrun Error flag has
Each UART baud rate is determined by either a fixed division of the
oscillator (in UART modes 0 and 2) or by the timer 1 or timer 2
overflow rate (in UART modes 1 and 3).
Timer 1 defaults to clock both UART0 and UART1. Timer 2 can be
programmed to clock either UART0 through T2CON (via bits R0CLK
and T0CLK) or UART1 through T2MOD (via bits R1CLK and
T1CLK). In this case, the UART not clocked by T2 could use T1 as
the clock source.
The serial port receive and transmit registers are both accessed at
Special Function Register SnBUF. Writing to SnBUF loads the
transmit register, and reading SnBUF accesses a physically
separate receive register.
The serial port can operate in 4 modes:
Mode 0: Serial I/O expansion mode. Serial data enters and exitsthrough RxDn. TxDn outputs the shift clock. 8 bits are
transmitted/received (LSB first). (The baud rate is fixed at 1/16 the
oscillator frequency.)
Mode 1: Standard 8-bit UART mode. 10 bits are transmitted(through TxDn) or received (through RxDn): a start bit (0), 8 data
bits (LSB first), and a stop bit (1). On receive, the stop bit goes into
RB8 in Special Function Register SnCON. The baud rate is variable.
Mode 2: Fixed rate 9-bit UART mode. 11 bits are transmitted(through TxD) or received (through RxD): start bit (0), 8 data bits
(LSB first), a programmable 9th data bit, and a stop bit (1). On
Transmit, the 9th data bit (TB8_n in SnCON) can be assigned the
value of 0 or 1. Or, for example, the parity bit (P, in the PSW) could
be moved into TB8_n. On receive, the 9th data bit goes into RB8_n
in Special Function Register SnCON, while the stop bit is ignored.
The baud rate is programmable to 1/32 of the oscillator frequency.
Mode 3: Standard 9-bit UART mode. 11 bits are transmitted(through TxDn) or received (through RxDn): a start bit (0), 8 data
bits (LSB first), a programmable 9th data bit, and a stop bit (1).
In fact, Mode 3 is the same as Mode 2 in all respects except baud
rate. The baud rate in Mode 3 is variable.
In all four modes, transmission is initiated by any instruction that
uses SnBUF as a destination register. Reception is initiated in
Mode 0 by the condition RI_n = 0 and REN_n = 1. Reception is
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
Serial Port Control RegisterThe serial port control and status register is the Special Function
Register SnCON, shown in Figure 12. This register contains not only
the mode selection bits, but also the 9th data bit for transmit and
receive (TB8_n and RB8_n), and the serial port interrupt bits (TI_n
and RI_n).
TI FlagIn order to allow easy use of the double buffered UART transmitter
feature, the TI_n flag is set by the UART hardware under two
conditions. The first condition is the completion of any byte
transmission. This occurs at the end of the stop bit in modes 1, 2, or
3, or at the end of the eighth data bit in mode 0. The second
condition is when SnBUF is written while the UART transmitter is
idle. In this case, the TI_n flag is set in order to indicate that the
second UART transmitter buffer is still available.
Typically, UART transmitters generate one interrupt per byte
transmitted. In the case of the XA UART, one additional interrupt is
generated as defined by the stated conditions for setting the TI_n
flag. This additional interrupt does not occur if double buffering is
bypassed as explained below. Note that if a character oriented
approach is used to transmit data through the UART, there could be
a second interrupt for each character transmitted, depending on the
timing of the writes to SBUF. For this reason, it is generally better to
bypass double buffering when the UART transmitter is used in
character oriented mode. This is also true if the UART is polled
rather than interrupt driven, and when transmission is character
oriented rather than message or string oriented. The interrupt occurs
at the end of the last byte transmitted when the UART becomes idle.
Among other things, this allows a program to determine when a
message has been transmitted completely. The interrupt service
routine should handle this additional interrupt.
The recommended method of using the double buffering in the
application program is to have the interrupt service routine handle a
single byte for each interrupt occurrence. In this manner the
program essentially does not require any special considerations for
double buffering. Unless higher priority interrupts cause delays in
the servicing of the UART transmitter interrupt, the double buffering
will result in transmitted bytes being tightly packed with no
intervening gaps.
9-bit ModePlease note that the ninth data bit (TB8) is not double buffered. Care
must be taken to insure that the TB8 bit contains the intended data
at the point where it is transmitted. Double buffering of the UART
transmitter may be bypassed as a simple means of synchronizing
TB8 to the rest of the data stream.
Bypassing Double BufferingThe UART transmitter may be used as if it is single buffered. The
recommended UART transmitter interrupt service routine (ISR)
technique to bypass double buffering first clears the TI_n flag upon
entry into the ISR, as in standard practice. This clears the interrupt
that activated the ISR. Secondly, the TI_n flag is cleared
immediately following each write to SnBUF. This clears the interrupt
flag that would otherwise direct the program to write to the second
transmitter buffer. If there is any possibility that a higher priority
interrupt might become active between the write to SnBUF and the
clearing of the TI_n flag, the interrupt system may have to be
temporarily disabled during that sequence by clearing, then setting
the EA bit in the IEL register.
Note Regarding Older XA-G30 DevicesOlder versions of the XA-G30, XA-G37, and XA-G35 emulation
bondout devices do not have the double buffering feature enabled.
Contact factory for details.
Philips Semiconductors Product data
XA-G30XA 16-bit microcontroller family
512 B RAM, watchdog, 2 UARTs
CLOCKING SCHEME/BAUD RATE GENERATIONThe XA UARTS clock rates are determined by either a fixed division
(modes 0 and 2) of the oscillator clock or by the Timer 1 or Timer 2
overflow rate (modes 1 and 3).
The clock for the UARTs in XA runs at 16x the Baud rate. If the
timers are used as the source for Baud Clock, since maximum
speed of timers/Baud Clock is Osc/4, the maximum baud rate is
timer overflow divided by 16 i.e. Osc/64.
In Mode 0, it is fixed at Osc/16. In Mode 2, however, the fixed rate is
Osc/32.
Baud Rate for UART Mode 0:Baud_Rate = Osc/16
Baud Rate calculation for UART Mode 1 and 3: Baud_Rate = Timer_Rate/16
Timer_Rate = Osc/(N*(Timer_Range– Timer_Reload_Value))
where N = the TCLK prescaler value: 4, 16, or 64.
and Timer_Range = 256 for timer 1 in mode 2.
65536 for timer 1 in mode 0 and timer 2
in count up mode.
The timer reload value may be calculated as follows:
Timer_Reload_Value = Timer_Range–(Osc/(Baud_Rate*N*16))
NOTES: The maximum baud rate for a UART in mode 1 or 3 is Osc/64. The lowest possible baud rate (for a given oscillator frequency
and N value) may be found by using a timer reload value of 0. The timer reload value may never be larger than the timer range. If a timer reload value calculation gives a negative or fractional
result, the baud rate requested is not possible at the given
oscillator frequency and N value.
Baud Rate for UART Mode 2: Baud_Rate = Osc/32
Using Timer 2 to Generate Baud RatesTimer T2 is a 16-bit up/down counter in XA. As a baud rate
generator, timer 2 is selected as a clock source for either/both
UART0 and UART1 transmitters and/or receivers by setting TCLKn
and/or RCLKn in T2CON and T2MOD. As the baud rate generator,
T2 is incremented as Osc/N where N = 4, 16 or 64 depending on
TCLK as programmed in the SCR bits PT1, and PTO. So, if T2 is
the source of one UART, the other UART could be clocked by either
T1 overflow or fixed clock, and the UARTs could run independently
with different baud rates.
Prescaler Select for Timer Clock (TCLK)
