4 8-bit timer/event counters 1 and 2 operations, 1 8-bit timer/event counter mode – NEC uPD78P078 User Manual

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

9.4 8-Bit Timer/Event Counters 1 and 2 Operations

9.4.1 8-bit timer/event counter mode

(1) Interval timer operations

The 8-bit timer/event counters 1 and 2 operate as interval timers which generate interrupt requests

repeatedly at intervals of the count value preset to 8-bit compare registers 10 and 20 (CR10 and CR20).

When the count values of the 8-bit timer registers 1 and 2 (TM1 and TM2) match the values set to CR10

and CR20, counting continues with the TM1 and TM2 values cleared to 0 and the interrupt request signals

(INTTM1 and INTTM2) are generated.

Count clock of the TM1 can be selected with bits 0 to 3 (TCL10 to TCL13) of the timer clock select register

1 (TCL1). Count clock of the TM2 can be selected with bits 4 to 7 (TCL14 to TCL17) of the timer clock select

register 1 (TCL1).

For the operation in the case the value of the compare register is changed during the timer count operation,

refer to 9.5 8-Bit Timer/Event Counters 1 and 2 Precautions (3).

Figure 9-8. Interval Timer Operation Timing

Remark

Interval time = (N + 1) x t : N = 00H to FFH

Count Clock

TM1 Count Value

INTTM1

CR10

TO1

Interval Time

Interval Time

Interval Time

Interrupt Request Acknowledge

Interrupt Request Acknowledge

N

N

N

N

Count Start

Clear

Clear

t

00

01

N

00

01

N

00

01

N

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