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AT89C51ID2
4289C–8051–11/05
Table 30. 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 31 &
Table 31. CCAPnH Registers (n = 0-4)
CCAP0H - PCA Module 0 Compare/Capture Control Register High (0FAh)
CCAP1H - PCA Module 1 Compare/Capture Control Register High (0FBh)
CCAP2H - PCA Module 2 Compare/Capture Control Register High (0FCh)
CCAP3H - PCA Module 3 Compare/Capture Control Register High (0FDh)
CCAP4H - PCA Module 4 Compare/Capture Control Register High (0FEh)
Reset Value = 0000 0000b
Not bit addressable
ECOMn
CAPPn
CAPNn
MATn
TOGn
PWMm
ECCFn
Module Function
0
000
No Operation
X
100
00
X
16-bit capture by a positive-edge
trigger on CEXn
X
010
00
X
16-bit capture by a negative trigger
on CEXn
X
110
00
X
16-bit capture by a transition on
CEXn
1
001
00
X
16-bit Software Timer / Compare
mode.
1
0
1
0
X
16-bit High Speed Output
1
000
010
8-bit PWM
1
0
1
X
0
X
Watchdog Timer (module 4 only)
76
543
210
--
----
--
Bit
Number
Bit
Mnemonic
Description
7-0
-
PCA Module n Compare/Capture Control
CCAPnH Value