MR82C54/B Intersil, MR82C54/B Datasheet - Page 5

• Manufacturer Part Number: MR82C54/B
• Manufacturer: Intersil
• Type: Programmabler

Specifications of MR82C54/B

• # Internal Timers: Single
• Propagation Delay Time: 260ns
• Operating Supply Voltage (min): 4.5V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Package Type: CLCC
• High Level Output Current: -2.5mA
• Low Level Output Current: 2.5mA
• Pin Count: 28
• Operating Temp Range: -55C to 125C
• Operating Temperature Classification: Military
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Not Compliant

Operational Description
General
After power-up, the state of the 82C54 is undefined. The
Mode, count value, and output of all Counters are undefined.
How each Counter operates is determined when it is pro-
grammed. Each Counter must be programmed before it can
be used. Unused counters need not be programmed.
Programming the 82C54
Counters are programmed by writing a Control Word and
then an initial count.
All Control Words are written into the Control Word Register,
which is selected when A1, A0 = 11. The Control Word spec-
ifies which Counter is being programmed.
By contrast, initial counts are written into the Counters, not
the Control Word Register. The A1, A0 inputs are used to
select the Counter to be written into. The format of the initial
count is determined by the Control Word used.
Write Operations
The programming procedure for the 82C54 is very flexible.
Only two conventions need to be remembered:
1. For Each Counter, the Control Word must be written
2. The initial count must follow the count format specified in the
Since the Control Word Register and the three Counters have
separate addresses (selected by the A1, A0 inputs), and each
Control Word specifies the Counter it applies to (SC0, SC1 bits),
no special instruction sequence is required. Any programming
sequence that follows the conventions above is acceptable.
before the initial count is written.
Control Word (least significant byte only, most significant
byte only, or least significant byte and then most significant
byte).
OUT GATECLK
A1
COUNTER
FIGURE 4. 82C54 SYSTEM INTERFACE
A1
A0
0
A0
CS
ADDRESS BUS (16)
OUT GATECLK
CONTROL BUS
DATA BUS (8)
COUNTER
D0 - D7
82C54
1
8
OUT GATECLK
COUNTER
RD
2
I/OR I/OW
WR
82C54
5
Control Word Format
A1, A0 = 11; CS = 0; RD = 1; WR = 0
SC - Select Counter
RW - Read/Write
M - Mode
BCD - Binary Coded Decimal
NOTE: Don’t Care bits (X) should be 0 to insure compatibility with
Possible Programming Sequence
RW1 RW0
Control Word - Counter 0
LSB of Count - Counter 0
MSB of Count - Counter 0
Control Word - Counter 1
LSB of Count - Counter 1
MSB of Count - Counter 1
Control Word - Counter 2
LSB of Count - Counter 2
MSB of Count - Counter 2
SC1
M2
D7
0
0
1
1
SC1
0
0
X
X
1
1
0
0
1
1
0
1
future products.
0
1
0
1
M1
SC0
0
0
1
1
0
0
Binary Counter 16-bit
Binary Coded Decimal (BCD) Counter (4 Decades)
D6
SC0
Counter Latch Command (See Read Operations)
Read/Write least significant byte only.
Read/Write most significant byte only.
Read/Write least significant byte first, then most
significant byte.
0
1
0
1
M0
0
1
0
1
0
1
RW1
D5
Select Counter 0
Select Counter 1
Select Counter 2
Read-Back Command (See Read Operations)
Mode 0
Mode 1
Mode 2
Mode 3
Mode 4
Mode 5
RW0
D4
D3
M2
M1
D2
A1
1
0
0
1
0
0
1
1
1
D1
M0
BCD
A0
D0
1
0
0
1
1
1
1
0
0