|
| PIN DIAGRAM OF MICROPROCESSOR 8085 |
Pin Diagram of Microprocessor 8085
The function of f Pin Diagram Microprocessor 8085
1] AD0 – AD7 Multiplexed Address/Data Bus
a) These are 8-bit bidirectional pins to carry address as well as data.
b) The lower order 8-bit Address signal is multiplexed with the bus.
b) The lower order 8-bit Address signal is multiplexed with the bus.
2] A8 – A15 Address Bus
a) These are 8-bit output unidirectional pins use to carry higher-order address signals at 16-bit
address.
b) These are not multiplexed with the data bus.
address.
b) These are not multiplexed with the data bus.
3] ALE (Address Latch Enable)
a) This is an output signal used to inform that the contents on AD0 – AD7 line is the lower line
of the 8-bit address of 16-bit address when ALE goes high.
b) When ALE is low it indicates the content on AD0 – AD7 line is 8-bit data.
c) ALE Signal is used to separate address signal from data signal that is A0-A7 and D0-D7
from AD0 – AD7.
of the 8-bit address of 16-bit address when ALE goes high.
b) When ALE is low it indicates the content on AD0 – AD7 line is 8-bit data.
c) ALE Signal is used to separate address signal from data signal that is A0-A7 and D0-D7
from AD0 – AD7.
4] IO/M
a) This is an output status signal used to give the status of operation performed with
memory or I/O by the microprocessor.
b) When I/M is low, the Microprocessor is performing operations related to memory.
c) When IO/M is high, the microprocessor is performing operations related to the I/O device.
memory or I/O by the microprocessor.
b) When I/M is low, the Microprocessor is performing operations related to memory.
c) When IO/M is high, the microprocessor is performing operations related to the I/O device.
5] Ready (READY)
a) This is an active-high input control signal and use by the microprocessor to checkwhether a
peripheral is ready or not for data transfer.
b) If the READY pin is high the microprocessor completes the operation and proceeds for thenext
operation.
c) When the READY pin is low microprocessor wait until it goes high.
peripheral is ready or not for data transfer.
b) If the READY pin is high the microprocessor completes the operation and proceeds for thenext
operation.
c) When the READY pin is low microprocessor wait until it goes high.
6] RD (READ)
This is an active low output control signal used to read data from memory or I/O devices
generated by the microprocessor.
generated by the microprocessor.
7] WR (Write)
This is an active low output control signal used to write data to memory or I/O devicesgenerated by the microprocessor.
8] Vcc (Power Supply Pin)
It is input pin through this pin +5V is applied to microprocessor 8085 IC.
9] S0, S1 ( Status Signal)
These are status signals which distinguish various operations given in the table.
S1 S0 Operation
0 0 HALT
0 1 WRITE
1 0 READ
1 1 FETCH
S1 S0 Operation
0 0 HALT
0 1 WRITE
1 0 READ
1 1 FETCH
10] RESET IN (Reset Input )
a) This is an active low input reset signal used to reset the microprocessor.
b) When this signal is received by the microprocessor clear program counter
I.e., 0000 and makes address data and control start execution from memory location
from 0000H onwards.
b) When this signal is received by the microprocessor clear program counter
I.e., 0000 and makes address data and control start execution from memory location
from 0000H onwards.
11] SID and SOD ( Serial Input Data and Output Data)
a) SID & SOD are active high input and output serial port pins respectively.
b) The data can be accepted from the SID pin.
c) The data can be transfer on a SOD pin.
b) The data can be accepted from the SID pin.
c) The data can be transfer on a SOD pin.
13] HOLD and HLDA
HOLD
a) It is an active-high input signal any peripheral device request on HOLD pin of
microprocessor 8085 for their address and data line.
b) When the HOLD pin is activated by an external signal the microprocessor release
bus control and allows the external peripheral to use them.
a) It is an active-high input signal any peripheral device request on HOLD pin of
microprocessor 8085 for their address and data line.
b) When the HOLD pin is activated by an external signal the microprocessor release
bus control and allows the external peripheral to use them.
HLDA
If microprocessor 8085 receives HOLD request then it acknowledges peripheralby HLDA pin.
14] TRAP
a) This is an actor who has to interrupt the control signal.
b) It is non mass cable interrupter.
c) It has the highest priority it need not be enabled and cannot be disabled.
d) When TRAP occurs then the microprocessor starts execution from 0024H automatically.
b) It is non mass cable interrupter.
c) It has the highest priority it need not be enabled and cannot be disabled.
d) When TRAP occurs then the microprocessor starts execution from 0024H automatically.
15] RST 7.5, RST 6.5, RST 5.5
This active high mass cable interrupter.
a) RST 7.5 has a second priority.
b) RST 6.5 has a third priority.
c) RST 5.5 has a fourth priority.
d) When RST 7.5, RST 6.5, RST 5.5 occurs then the microprocessor transfer programscontrol tovector address 003CH,0034H, and 002CH respectively.
a) RST 7.5 has a second priority.
b) RST 6.5 has a third priority.
c) RST 5.5 has a fourth priority.
d) When RST 7.5, RST 6.5, RST 5.5 occurs then the microprocessor transfer programscontrol tovector address 003CH,0034H, and 002CH respectively.
16] INTA_ and INTR
a) INTR is an active-high interrupt signal.
b) It has the lowest priority.
c) It is mass cable interrupter.
d) When INTR occurs the microprocessor generates an interrupt acknowledge signal INTA_.
b) It has the lowest priority.
c) It is mass cable interrupter.
d) When INTR occurs the microprocessor generates an interrupt acknowledge signal INTA_.
17] CLK OUT
a) It is an output pin.
b) In many applications some digital ICs require a clock signal to drive themself.
c) The clock signal for driving these digital ICs is obtained from CLK OUT ofmicroprocessor 8085.
b) In many applications some digital ICs require a clock signal to drive themself.
c) The clock signal for driving these digital ICs is obtained from CLK OUT ofmicroprocessor 8085.
18] X1 and X2
This terminal is to be connected to an external cry5 oscillator which drives an internal
circuit of the microprocessor to produce a suitable clock for the operation of
microprocessor.
circuit of the microprocessor to produce a suitable clock for the operation of
microprocessor.
Special thanks: Aniket Narnaware
Read more:-
