NEC PD78078 用户手册

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CHAPTER 9 8-BIT TIMER/EVENT COUNTERS 1 AND 2

9.5 8-Bit Timer/Event Counters 1 and 2 Precautions

(1) Timer start errors

An error with a maximum of one clock may occur concerning the time required for a match signal to be gener-

ated after timer start. This is because 8-bit timer registers 1 and 2 (TM1 and TM2) are started asynchronously

with the count pulse.

Figure 9-13. 8-Bit Timer Registers 1 and 2 Start Timing

(2) 8-bit compare register 10 and 20 setting

The 8-bit compare registers 10 and 20 (CR10 and CR20) can be set to 00H.

Thus, when these 8-bit compare registers are used as event counters, one-pulse count operation can be

carried out.

When the 8-bit compare register is 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 1 to 0 and stopping timer operation.

Figure 9-14. External Event Counter Operation Timing

Count Pulse

TM1, TM2 Count Value

00H

01H

02H

03H

04H

Timer Start

TI1, TI2, Input

CR10, CR20

TM1, TM2 Count Value

TO1, TO2

Interrupt Request Flag

00H