T89C51RD2-3CBC-L ATMEL [ATMEL Corporation], T89C51RD2-3CBC-L Datasheet - Page 29

• Manufacturer Part Number: T89C51RD2-3CBC-L
• Description: 0 to 40MHz Flash Programmable 8-bit Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

T89C51RD2
Before enabling ECOM bit, CCAPnL and CCAPnH should be set with a non zero value, otherwise an unwanted
match could happen. Writing to CCAPnH will set the ECOM bit.
Once ECOM set, writing CCAPnL will clear ECOM so that an unwanted match doesn’t occur while modifying
the compare value. Writing to CCAPnH will set ECOM. For this reason, user software should write CCAPnL first,
and then CCAPnH. Of course, the ECOM bit can still be controlled by accessing to CCAPMn register.
6.5.3. High Speed Output Mode
In this mode the CEX output (on port 1) associated with the PCA module will toggle each time a match occurs
between the PCA counter and the module's capture registers. To activate this mode the TOG, MAT, and ECOM
bits in the module's CCAPMn SFR must be set (See Figure 11).
A prior write must be done to CCAPnL and CCAPnH before writing the ECOMn bit.
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CCAPnH
Write to
1
CCAPnL
Write to
0
Reset
Enable
*
Figure 10. PCA Compare Mode and PCA Watchdog Timer
Only for Module 4
CCAPnH
CH
PCA counter/timer
16 bit comparator
CIDL
CF
ECOMn
WDTE
CCAPnL
CR
CL
CAPPn
Match
CAPNn MATn TOGn PWMn ECCFn
CCF4
CCF3
CCF2
CPS1
CCF1
CPS0
Rev. F - 15 February, 2001
CCF0
ECF
CCON
0xD8
CCAPMn, n = 0 to 4
0xDA to 0xDE
CMOD
0xD9
PCA IT
RESET *