Rainbow Electronics T89C51RD2 User Manual
Page 26
Rev. F - 15 February, 2001
26
T89C51RD2
Table 9. CCAPMn: PCA Modules Compare/Capture Control Registers
Table 10. PCA Module Modes (CCAPMn Registers)
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 (See Table 11 & Table 12)
CCAPMn Address
n = 0 - 4
CCAPM0=0DAH
CCAPM1=0DBH
CCAPM2=0DCH
CCAPM3=0DDH
CCAPM4=0DEH
-
ECOMn
CAPPn
CAPNn
MATn
TOGn
PWMm
ECCFn
Reset value
X
0
0
0
0
0
0
0
Symbol
Function
-
Not implemented, reserved for future use.
a
a.
User software should not write 1s to reserved bits. These bits may be used in future 8051 family
products to invoke new features. In that case, the reset or inactive value of the new bit will be 0, and its
active value will be 1. The value read from a reserved bit is indeterminate.
ECOMn
Enable Comparator. ECOMn = 1 enables the comparator function.
CAPPn
Capture Positive, CAPPn = 1 enables positive edge capture.
CAPNn
Capture Negative, CAPNn = 1 enables negative edge capture.
MATn
Match. When MATn = 1, a match of the PCA counter with this module's compare/capture
register causes the CCFn bit in CCON to be set, flagging an interrupt.
TOGn
Toggle. When TOGn = 1, a match of the PCA counter with this module's compare/capture
register causes the CEXn pin to toggle.
PWMn
Pulse Width Modulation Mode. PWMn = 1 enables the CEXn pin to be used as a pulse width
modulated output.
ECCFn
Enable CCF interrupt. Enables compare/capture flag CCFn in the CCON register to generate
an interrupt.
ECOMn
CAPPn
CAPNn
MATn
TOGn
PWMm
ECCFn
Module Function
0
0
0
0
0
0
0
No Operation
X
1
0
0
0
0
X
16-bit capture by a positive-edge
trigger on CEXn
X
0
1
0
0
0
X
16-bit capture by a negative trigger on
CEXn
X
1
1
0
0
0
X
16-bit capture by a transition on CEXn
1
0
0
1
0
0
X
16-bit Software Timer / Compare
mode.
1
0
0
1
1
0
X
16-bit High Speed Output
1
0
0
0
0
1
0
8-bit PWM
1
0
0
1
X
0
X
Watchdog Timer (module 4 only)