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MSM82C54-2RS/GS/JS

(3) Read Back Command Operation

Use of the read back command enables the user to check the count value, program mode,

output pin state and null count flag of the selected counter.

The command is written in the control word register, and the format is as shown below. For

It is possible to latch multiple counters by using the read back command. Latching of a read

counter is automatically canceled but other counters are kept latched. If multiple read back

commands are written for the same counter, commands other than the first one are ignored.

It is also possible to latch the status information of each counter by using the read back

command. The status of a certain counter is read when the counter is read. The counter

status format is as follows:

Use of this bit makes it possible to monitor the counter output, so the corresponding

hardware may be omitted.

OUTPUT

NULL

COUNT

RL1

RL0

M2

M1

M0

BCD

0 = Output pin status is 0.

0 = Count value reading is effective

(See the control word format.)

1

1

COUNT

STATUS

CNT2

CNT1

CNT0

0