CDP1857C_1 Datasheet, PDF (1/5 Pages) Intersil Corporation – 4-Bit Bus Buffer/Separator

TM
CDP1857C
March 1997
4-Bit Bus Buffer/Separator
Features
• Provides Easy Connection of I/O to CDP1800-Series
Microprocessor Data Bus
• Non-Inverting Fully Buffered Data Transfer
Ordering Information
PART
NUMBER
CDP1857CE
CDP1857CD
TEMP. RANGE
-40^oC to +85^oC
-40^oC to +85^oC
PACKAGE
PDIP
SBDIP
PKG. NO.
E16.3
D16.3
TABLE 1. CDP1857 FUNCTION FOR I/O BUS SEPARATOR
OPERATION
CS MRD
DATA BUS OUT
DB0-DB3
DATA OUT
DO0-DO3
0
X
High Impedance
High Impedance
1
0
High Impedance
Data Bus
1
1
Data In
High Impedance
Description
The CDP1857C is a 4-bit CMOS non-inverting bus separator
designed for use in CDP1800-series microprocessor systems. It can
be controlled directly by a 1800-series microprocessor without the
use of additional components.
The CDP1857 is designed for use as a bus buffer or separator
between the 1800-series microprocessor data bus and I/O devices.
It provides a chip-select (CS) input signal which, when high (1),
enables the bus-separator three-state output drivers. The direction
of data flow, when enabled, is controlled by the MRD input signal.
In the CDP1857, when MRD = 1, it enables the three-state bus driv-
ers (DB0-DB3) and transfers data from the DATA-IN lines onto the
data bus. When MRD = 0, it disables the three-state bus drivers
(DB0-DB3) and enables the three-state data output drivers (DO0-
DO3), thus, transferring data from the data bus to the DATA-OUT ter-
minals.
The CDP1857 can be used as a bidirectional bus buffer by connect-
ing the corresponding DI and DO terminals (Figure 1). The MRD out-
put signal from the 1800-series microprocessor has the correct
polarity to control the CDP1857 when it is used as I/O bus buffer/sep-
arator. Therefore, the 1800-series microprocessor MRD signal can be
connected directly to the MRD input of CDP1857. See Function Table
1 for use of the CDP1857 as an I/O bus buffer/separator.
The CDP1857C is supplied in 16-lead hermetic, dual-in-line ceramic
packages (D suffix), and in 16-lead plastic packages (E suffix).
Pinout
16 LEAD DIP
TOP VIEW
DI0 1
DI1 2
DO0 3
DO1 4
DO2 5
DO3 6
DI2 7
V_SS 8
16 V_DD
15 CS
14 DB0
13 DB1
12 DB2
11 DB3
10 MRD
9 DI3
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Copyright © Intersil Americas Inc. 2001. All Rights Reserved
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File Number 1192.2