msm82c54-2rs Oki Semiconductor, msm82c54-2rs Datasheet - Page 18

• Manufacturer Part Number: msm82c54-2rs
• Description: Cmos Programmable Interval Timer
• Manufacturer: Oki Semiconductor

¡ Semiconductor
(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
this command, the counter selection occurs according to bits D
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:
Bits D
Bit D
Use of this bit makes it possible to monitor the counter output, so the corresponding
hardware may be omitted.
7
5
indicates the status of the output pin.
to D
OUTPUT
0
D
1
indicate the mode programmed by the most recently written control word.
D
7
7
COUNT
NULL
D
1
D
6
6
D
D
D
D
D
D
(CS=0, A
D
D
D
COUNT
5
4
3
2
1
0
: 0 = Selected counter latch operation
: 0 = Selected counter status latch operation
: 1 = Counter #2 selection
: 1 = Counter #1 selection
: 1 = Counter #0 selection
: 0
7
6
5
D
: 1 = Output pin status is 1.
: 1 = Null count
RL1
- D
D
5
=
0 = Output pin status is 0.
0 = Count value reading is effective
5
0
Fixed
: Programmed mode of counter
(See the control word format.)
0
, A
STATUS
1
D
=1, RD=1, WR=0)
RL0
D
4
4
CNT2
D
M2
D
3
3
CNT1
D
M1
D
2
2
CNT0
D
3
M0
D
1
, D
MSM82C54-2RS/GS/JS
1
2
and D
D
BCD
0
D
0
0
1
.
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