CMP82C55AZ datasheet(9/26 Pages) INTERSIL

9 / 26 page

FN6140.2

June 15, 2006

Operating Modes

Mode 1 - (Strobed Input/Output). This functional configuration

provides a means for transferring I/O data to or from a specified

port in conjunction with strobes or “hand shaking” signals. In

mode 1, port A and port B use the lines on port C to generate or

accept these “hand shaking” signals.

Mode 1 Basic Function Definitions:

• Two Groups (Group A and Group B)

• Each group contains one 8-bit port and one 4-bit control/data

port

• The 8-bit data port can be either input or output. Both inputs

and outputs are latched.

• The 4-bit port is used for control and status of the 8-bit port.

Input Control Signal Definition

(Figures 6 and 7)

STB (Strobe Input)

A “low” on this input loads data into the input latch.

IBF (Input Buffer Full F/F)

A “high” on this output indicates that the data has been loaded

into the input latch: in essence, an acknowledgment. IBF is set

by STB input being low and is reset by the rising edge of the

RD input.

INTR (Interrupt Request)

A “high” on this output can be used to interrupt the CPU when

an input device is requesting service. INTR is set by the

condition: STB is a “one”, IBF is a “one” and INTE is a “one”. It

is reset by the falling edge of RD. This procedure allows an

input device to request service from the CPU by simply strobing

its data into the port.

INTE A

Controlled by bit set/reset of PC4.

INTE B

Controlled by bit set/reset of PC2.

Output Control Signal Definition

(Figure 8 and 9)

OBF - (Output Buffer Full F/F). The OBF output will go “low”

to indicate that the CPU has written data out to the specified

port. This does not mean valid data is sent out of the port at this

time since OBF can go true before data is available. Data is

guaranteed valid at the rising edge of OBF, (See Note 1). The

OBF F/F will be set by the rising edge of the WR input and reset

by ACK input being low.

CONTROL WORD #13

CONTROL WORD #15

Mode 0 Configurations (Continued)

PA7 - PA0

PC7 - PC4

PC3 - PC0

PB7 - PB0

D7 - D0

82C55A

PA7 - PA0

PC7 - PC4

PC3 - PC0

PB7 - PB0

D7 - D0

82C55A

MS82C55A, MQ82C55A, MP82C55A

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