8-Bit Timer/Event Counter Operating Precautions - NEC mPD780208 Subseries User Manual

7.5 8-Bit Timer/Event Counter Operating Precautions

(1) Timer start error
An error of up to one clock may occur in the time required for a match signal to be generated after timer
start. This is because 8-bit timer registers 1 and 2 (TM1 and TM2) are started asynchronously to the count
pulse.
Count pulse
TM1, TM2 count value
(2) 8-bit compare registers 1 and 2 settings
The 8-bit compare registers (CR10 and CR20) can be set to 00H.
Thus, when an 8-bit compare register is used as an event counter, a one-pulse count operation can be
carried out.
When the 8-bit compare registers are used as a 16-bit timer/event counter, write data to CR10 and CR20
after setting bit 0 (TCE1) of the 8-bit timer mode control register (TMC1) to 0 and stopping timer operation.
TI1, TI2 input
CR10, CR20
TM1, TM2 count value
TO1, TO2
Interrupt request signal
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CHAPTER 7 8-BIT TIMER/EVENT COUNTER
Figure 7-14. 8-Bit Timer Register Start Timing
00H 01H
Timer start
Figure 7-15. External Event Counter Operation Timing
User's Manual U11302EJ4V0UM
02H
00H
00H 00H
03H 04H
00H 00H