UPD67B datasheet(23/73 Pages) RENESAS

23 / 73 page

µPD67B, 68B

Data Sheet U16792EJ1V1DS

4.2 Timer Operation

The timer starts (counting down) when a value other than 0 is set for the down counter with a timer manipulation

instruction. The timer manipulation instructions for making the timer start operation are shown below.

MOV T0, A

MOV T1, A

MOV T, #data10

MOV T, @R0

The down counter is decremented (–1) in the cycle of 64/fX. If the value of the down counter becomes 0, the

zero detector generates the timer operation end signal to stop the timer operation. At this time, if the timer is in

HALT mode (HALT #

×101B) waiting for the timer to stop its operation, the HALT mode is released and the instruction

following the HALT instruction is executed. The output of the timer operation end signal is continued while the down

counter is 0 and the timer is stopped. The following relational expression applies between the timer’s output time

and the down counter’s set value.

Timer output time = (Set value + 1)

× 64/fX – 4/fX

In addition, when the timer is set successively, the timer output time is also 4/fX shorter than the total time. An

example is shown below.

Example

When fX = 4 MHz

MOV T, #3FFH

STTS #05H

HALT #05H

MOV T, #232H

STTS #05H

HALT #05H

In the case above, the timer output time is as follows.

(Set value + 1)

× 64/fX + (Set value + 1) × 64/fX – 4/fX

= (511 + 1)

× 64/4 + (50 + 1) × 64/4 – 4/4

= 9.007 ms

UPD67B Datasheet(PDF) 23 Page - Renesas Technology Corp