IDT73720 /A16-BIT TRI-PORT BUS EXCHANGER

COMMERCIAL TEMPERATURE RANGE

11.5

3

PIN DESCRIPTION

Signal

I/O

Description

X(0:15)

I/O

Bidirectional Data Port X. Usually connected to the CPU's A/D (Address/Data) bus.

Y(0:15)

I/O

Bidirectional Data port Y. Connected to the even path or even bank of memory.

Z(0:15)

I/O

Bidirectional Data port Z. Connected to the odd path or odd bank of memory.

LEXY

I

Latch Enable input for Y-Write Latch. The Y-Write Latch is open when LEXY is HIGH. Data from the X-port

(CPU) is latched on the HIGH-to-LOW transition of LEXY

LEXZ

I

Latch Enable input for Z-Write Latch. The Z-Write Latch is open when LEXZ is HIGH. Data from the X-port

(CPU) is latched on the HIGH-to-LOW transition of LEXZ.

LEYX

I

Latch Enable input for the Y-Read Latch. The Y-Read Latch is open when LEYX is HIGH. Data from the even

path Y is latched on the HIGH-to-LOW transition of LEYX.

LEZX

I

Latch Enable input for the Z-Read Latch. The Z-Read Latch is open when LEZX is HIGH. Data from the odd

path Z is latched on the HIGH-to-LOW transition of LEZX

PATH

I

Even/Odd Path Selection. When high, PATH enables data transfer between the X-Port and the Y-port (even

path). When LOW, PATH enables data transfer between the X-Port and the Z-Port (odd path).

T/

R

I

Transmit/Receive Data. When high, Port X is an input Port and either Port Y or Z is an output Port. When LOW,

Port X is an output Port while Ports Y & Z are input Ports

OEU

I

Output Enable for Upper byte. When LOW, the Upper byte of data is transfered to the port specified by PATH in

the direction specified by T/

R .

OEL

I

Output Enable for Lower byte. When LOW, the Lower byte of data is transfered to the port specified by PATH in

the direction specified by T/

R .

2527 tbl 02

Symbol

Conditions

Max.

Unit

Input Capacitance

8

pF

Output Capacitance

12

pF

NOTE:

2527 tbl 04

1. This parameter is guaranteed by device characterization, but is not prod-

uction tested.

ABSOLUTE MAXIMUM RATINGS

(1)

Symbol

Rating

Com’l.

Mil.

Unit

Terminal Voltage

–0.5 to +7.0

–0.5 to +7.0

V

with Respect

to GND

Operating

0 to +70

–55 to +125

°C

Temperature

Temperature

–55 to +125

–65 to +135

°C

Under Bias

Storage

–55 to +125

–65 to +125

°C

Temperature

Power

1.0

1.0

W

Dissipation

DC Output

50

50

mA

Current

NOTE:

2527 tbl 03

1. Stresses greater than those listed under ABSOLUTE MAXIMUM

RATINGS may cause permanent damage to the device. This is a stress

rating only and functional operation of the device at these or any other

conditions above those indicated in the operational sections of this

specification is not implied.

Exposure to absolute maximum rating

conditions for extended periods may affect reliability.

TRUTH TABLE

Path

T/

RR

OEU

OEU

OEL

OEL

Functionality

LL

LL

Z

LH

L

L

X

HL

L

L

Y

H

H

L

L

X

X

X

H

H

All output buffers are

disabled

X

X

H

L

Transfer of lower 8 bits

(0:7) as per PATH & T/

R

X

X

L

H

Transfer of upper 8 bits

(8:15) as per PATH & T/

R

NOTES:

2527 tbl 01

1. For Z

→X and X→Z transfers, Y-port output buffers are tristated.

2. For Y

→X and X→Y transfers, Z-port output buffers are tristated.