t89c51rd2-slscl ATMEL Corporation, t89c51rd2-slscl Datasheet - Page 30

• Manufacturer Part Number: t89c51rd2-slscl
• Description: 0 To 40 Mhz Flash Programmable 8-bit Microcontroller
• Manufacturer: ATMEL Corporation

Figure 10. PCA Compare Mode and PCA Watchdog Timer
High Speed Output Mode
30
CCAPnH
Write to
T89C51RD2
1
CCAPnL
Write to
0
Reset
Enable
*
Only for Module 4
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.
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.
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 CCF1 CCF0
CPS1 CPS0
ECF
CCON
0xD8
CCAPMn, n = 0 to 4
0xDA to 0xDE
CMOD
0xD9
PCA IT
RESET *
4243G–8051–05/03