NEC PD17062 User Manual

Page 137

137

PD17062

12.3.1 Example of Using the Timer Based on the BTM0CY Flag

An example of a program follows.

Example

INITFLG NOT BTM0ZX, NOT BTM0CK2, NOT BTM0CK1, NOT BTM0CK0

; Built-in macro

; Specifies that the timer carry FF be set at intervals of 100 ms.

LOOP1:

MOV M1, #0110B

LOOP2:

SKT1 BTM0CY

; Built-in macro

; Tests the BTM0CY flag. Branches to NEXT if the flag is 0.

ADD

M1, #0100B ; Adds 4 to data memory M1.

SKT1 CY

; Built-in macro

; Tests the CY flag.

; Branches to NEXT if the flag is 0.

Process A

; Performs process A if the flag is 1.

MOV M1, #0110B

Process B

; Performs process B and branches to LOOP.

LOOP

This program performs process A at intervals of one second.

Note the following point (1) when creating this program.

(1) The time interval at which the BTM0CY flag is checked must be less than the time interval at which the

timer carry FF is set to 1.

This is because if it takes 100 ms or longer to perform process B, it is impossible to detect when the timer

carry FF is set, as shown in Fig. 12-3.

Fig. 12-3 BTM0CY Flag Check and Timer Carry FF

(

SKT1
BTM0CY

Timer carry FF set pulse

BTM0CY flag

Process B

Process B'

Because it takes long to perform process B' after it is detected that the
BTM0CY flag is set at

$, it is impossible to detect when the BTM0CY

flag is set at