Instruction manual

Table Of Contents
Page
47
PC215E
5.3.18 Z2 Counter/Timer Status Register
This status register provides the means to interrogate the three sixteen bit counter/timers of the
82C54 Z2. An outline of its operation is given here, but reference should be made to the 82C54
device manufacturers’ data sheets in the appendix before programming of the counter is
attempted.
The Z2 counter Status Register is a READ register. The WRITE register at the same location
BA + 13
16
controls the operation of the 82C54 Counter/Timer Z2 and issues a Read-Back
command before the status is interrogated.
Register
Offset
Write and/or
Read
Register
Width
Register
Title
Mnemonic
17
16
Read 8 bits
82C54 Z2 Counter/Timer
Status Register
Z2 CTS
FUNCTION
When the Read-Back Command requests the status of the counters, the status register provides
the count value, programmed mode, the current state of the OUT pin and Null Count Flag of the
selected counter(s).
01234567
Binary or BCD
Binary Count (16 Bits)
BCD Count (4 Digits)
BCD
0
1
Count Mode
Mode 0
Mode 1
Mode 2
Mode 3
Mode 4
Mode 5
CM0
0
1
0
1
0
1
CM1
0
0
1
1
0
0
CM2
0
0
X
X
1
1
Read/Write Mode
Count Latch Command
Low Byte Only
High Byte Only
Low Byte then High Byte
RWM0
0
1
0
1
RWM1
0
0
1
1
Select Counter or MLC
Counter 0
Counter 1
Counter 2
Multiple Latch Command
SC0
0
1
0
1
SC1
0
0
1
1