XA-S3 NXP Semiconductors, XA-S3 Datasheet - Page 20
Manufacturer Part Number
The XA-S3 device is a member of Philips Semiconductors? XA(eXtended Architecture) family of high performance 16-bitsingle-chip microcontrollers
The XA-S3 has three general purpose counter/timers, two of which may
also be used as baud rate generators for either or both of the UARTs.
Timer 0 and 1
These are identical to the standard XA-G3 timer 0 and 1.
This is identical to the standard XA-G3 timer 2.
Programmable Counter Array (PCA)
The Programmable Counter Array available on the XA-S3 is a
special 16-bit Timer that has five 16-bit capture/compare modules
associated with it. Each of the modules can be programmed to
operate in one of four modes: rising and/or falling edge capture,
software timer, high-speed output, or pulse width modulator. Each
module has a pin associated with it in port 1. Module 0 is connected
to P4.1(CEX0), module 1 to P4.2(CEX1), etc. The basic PCA
configuration is shown in Figure 7.
The PCA timer is a common time base for all five modules and can
be programmed to run at: the TCLK rate (Osc/4, Osc/16, or Osc/64),
the Timer 0 overflow, or the input on the ECI pin (P4.0). When the
ECI input is used, the falling edge clocks the PCA counter. The timer
count source is determined from the CPS1 and CPS0 bits in the
CMOD SFR as follows (see Figure 10):
CPS1 CPS0 PCA Timer Count Source
In the CMOD SFR are three additional bits associated with the PCA.
They are CIDL which allows the PCA to stop during idle mode,
WDTE which enables or disables the watchdog function on
module 4, and ECF which when set causes an interrupt and the
PCA overflow flag CF (in the CCON SFR) to be set when the PCA
timer overflows. These functions are shown in Figure 8. In addition,
each PCA module may generate a separate interrupt.
The watchdog timer function is implemented in module 4 (see
2000 Dec 01
XA 16-bit microcontroller
32 K/1 K OTP/ROM/ROMless, 8-channel 8-bit A/D, low voltage (2.7 V–5.5 V),
C, 2 UARTs, 16 MB address range
16-BIT HIGH SPEED OUTPUT
WATCHDOG TIMER (MODULE 4 ONLY)
TCLK (Osc/4, Osc/16, or Osc/64)
Timer 0 overflow
ECI (PCA External Clock Input (max rate = Osc/4)
TIME BASE FOR PCA MODULES
Figure 7. Programmable Counter Array (PCA)
The CCON SFR contains the run control bit for the PCA and the
flags for the PCA timer (CF) and each module (refer to Figure 11).
To run the PCA the CR bit (CCON.6) must be set by software. The
PCA is shut off by clearing this bit. The CF bit (CCON.7) is set when
the PCA counter overflows and an interrupt will be generated if the
ECF bit in the CMOD register is set, The CF bit can only be cleared
by software. Bits 0 through 4 of the CCON register are the flags for
the modules (bit 0 for module 0, bit 1 for module 1, etc.) and are set
by hardware when either a match or a capture occurs. These flags
also can only be cleared by software. The PCA interrupt system
shown in Figure 9.
Each module in the PCA has a special function register associated
with it. These registers are: CCAPM0 for module 0, CCAPM1 for
module 1, etc. (see Figure 12). The registers contain the bits that
control the mode that each module will operate in. The ECCF bit
(CCAPMn.0 where n=0, 1, 2, 3, or 4 depending on the module)
enables the CCF flag in the CCON SFR to generate an interrupt
when a match or compare occurs in the associated module. PWM
(CCAPMn.1) enables the pulse width modulation mode. The TOG
bit (CCAPMn.2) when set causes the CEX output associated with
the module to toggle when there is a match between the PCA
counter and the module’s capture/compare register. The match bit
MAT (CCAPMn.3) when set will cause the CCFn bit in the CCON
register to be set when there is a match between the PCA counter
and the module’s capture/compare register.
The next two bits CAPN (CCAPMn.4) and CAPP (CCAPMn.5)
determine the edge that a capture input will be active on. The CAPN
bit enables the negative edge, and the CAPP bit enables the
positive edge. If both bits are set both edges will be enabled and a
capture will occur for either transition. The last bit in the register
ECOM (CCAPMn.6) when set enables the comparator function.
Figure 13 shows the CCAPMn settings for the various PCA
There are two additional registers associated with each of the PCA
modules. They are CCAPnH and CCAPnL and these are the
registers that store the 16-bit count when a capture occurs or a
compare should occur. When a module is used in the PWM mode
these registers are used to control the duty cycle of the output.