®
ISO-CMOS ST-BUS™ FAMILY
MT8920B
ST-BUS Parallel Access Circuit
Features
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High speed parallel access to the serial ST-BUS
Parallel bus optimized for 68000
µP
(mode 1)
Fast dual-port RAM access (mode 2)
Access time: 120 nsec
Parallel bus controller (mode 3) - no external
controller required
Flexible interrupt capabilities - two
independent/programmable interrupt sources
with auto-vectoring
Selectable 24 and 32 channel operation
Programmable loop-around modes
Low power CMOS technology
ISSUE 6
June 1996
Ordering Information
MT8920BE
28 Pin Plastic DIP
MT8920BC
28 Pin Ceramic DIP
MT8920BP
28 Pin Plastic J-Lead
MT8920BS
28 Pin SOIC
-40°C to 85°C
Description
The ST-BUS Parallel Access Circuit (STPA) provides
a simple interface between Mitel’s ST-BUS and
parallel system environments.
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Applications
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Parallel control/data access to T1/CEPT digital
trunk interfaces
Digital signal processor interface to ST-BUS
Computer to Digital PABX link
Voice store and forward systems
Interprocessor communications
D7-D0
A4-A0
Tx0
Dual Port Ram
32 X 8
Parallel-
to-serial
Converter
STo0
CS
DS, OE
R/W, WE
DTACK,
BUSY, DCS
IRQ, 24/32
IACK, MS1
A5, STCH
MMS
Rx0
Dual Port Ram
32 X 8
Parallel
Port
Interface
Interrupt
Registers
Control
Registers
Serial-to-
Parallel
Converter
STi0
Tx1
Dual Port Ram
32 X 8
Parallel-
to-Serial
Converter
Comp/
MUX
Address
Generator
STo1
F0i
C4i
V
SS
V
DD
Figure 1 - Functional Block Diagram
3-3
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