Cautions On 8-Bit Timer/Event Counter Operating - NEC 78014Y Series User Manual

9.5 Cautions on 8-Bit Timer/Event Counter Operating

(1) Timer start errors
An error of one clock maximum may occur concerning 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 with the
count pulse.
Count Pulse
TM1, TM2 Count Value
(2) 8-bit compare registers 1 and 2 sets
The 8-bit compare registers (CR10 and CR20) can be set to 00H.
Therefore, when the 8-bit compare register is used as event counter, one-pulse count operation can be carried
out.
When the 8-bit compare registers are used as 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.
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TI1, TI2 Input
CR10, CR20
TM1, TM2 Count Value
Interrupt Request Flag
220
CHAPTER 9 8-BIT TIMER/EVENT COUNTER
Figure 9-14. 8-Bit Timer Register Start Timings
00H
Timer Start
Figure 9-15. External Event Counter Operation Timings
TO1, TO2
01H 02H
00H
00H 00H
03H 04H
00H 00H