8155 Programmable Interface

Programmable Peripheral Interface Devices Support chips: chips: 8155 8155,, 8255 8255,, 8279, 8254, 8254, DMA Controller, Interrupt Controller, USART

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Programmable Interface Devices 

used to interface a I/O device to the microprocessor System Bus

8085

Programmable I/O Interface

I/O Devices









8155 – A multipurpose programmable interface Designed to be compatible with 8085  It includes 

 

256 bytes of Read/Write memory Three I/O ports 



Port A Port B









Block Diagram - 8155 RESET AD0-7

8 0 8 5

IO/M RD

Port A 8

256 X 8 Static RAM

A

8 Port B

B

8

WR ALE

PA0-7

Port C

PB0-7

I / O D e v i c e s









Application design with 8155 

Objectives  

Interfacing 8155 with 8085 Programming 8155









Interfacing 8085 with 8155 RESET AD0-7

Port A 8 CE

A15

256 X 8 Static RAM 8085

A

8 Port B

B

8

IO/M RD

Port C











Programming 8155 8155 is a Programmable Peripheral Interface  8085 can send data to 8155 using data bus 











What type of Commands can be given to 8155? To configure the I/O ports as Input or Output  To start/stop timer etc. 











Control word for 8155 

A command/instruction for 8155 is also called control word











Control Word Definition for 8155 D0 D1

Port A Port B

0, Input

1, Output

D3 D2 PORT C

0

0

ALT1

0

1

ALT2











I/O functions of Port C ALT AL T

D3 D2 PC5 PC4 PC3 PC2 PC1 PC0

ALT1 ALT1 0

0 I

I

I

I

I

I













Design an interfacing circuit to read data from an A/D



































































































8155 Programmable Interface

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