IBM nec pd78082 User Manual

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CHAPTER 6 8-BIT TIMER/EVENT COUNTERS 5 AND 6

6.5 Cautions on 8-Bit Timer/Event Counters 5 and 6

(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 5 and 6 (TM5 and TM6) are started asynchronously

with the count pulse.

Figure 6-18. 8-Bit Timer Registers 5 and 6 Start Timing

Count Pulse

TM5, TM6 Count Value

00H

01H

02H

03H

04H

Timer Start

TI5, TI6, Input

CR50, CR60

TM5, TM6 Count Value

TO5, TO6

Interrupt Request Flag

00H

(2) 8-bit compare register 50 and 60 setting

The 8-bit compare registers 50 and 60 (CR50 and CR60) 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.

Figure 6-19. External Event Counter Operation Timing