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IEEE-488 Option -05
Introduction
7
7-3
7-1. Introduction
The IEEE-488 Interface turns the Data Acquisition Unit 2620A into a fully
programmable instrument for use with the IEEE Standard 488.1 (1987) interface bus
(IEEE-488 bus). With the IEEE-488 Interface, the instrument can become part of an
automated instrumentation system.
The IEEE-488 Interface cannot be used with the Hydra Data Logger (2625A).
7-2. Theory of Operation
7-3. Functional Block Description
The IEEE-488 Assembly (A5) requires power supply voltages, address, data and control
signals from the instrument Main Assembly (A1) to operate. The A5 assembly
implements the circuitry necessary to satisfy the IEEE-488.1 standard for programmable
instrumentation.
7-4. IEEE-488 PCA Detailed Circuit Description (2620A Only)
The IEEE-488 PCA comprises the following functional blocks: the Main PCA
Connector, the IEEE-488 Controller, and the IEEE-488 Transceivers and Connector.
These three blocks are described in the following paragraphs. Refer to Section 8 for a
schematic diagram of the IEEE-488 PCA.
Pin numbering for the IEEE Controller (A5U1) differs somewhat on early production
units. All A5U1 pin references in this section relate to newer production units.
Differences for early production units can be identified by referencing the manufacturer’s
number on the A5U1 chip with the information provided in Table 7-1.
Table 7-1. A5U1 Pin Differences
WD9914 (Early Production A5U1) TMS9914A (Newer Production A5U1)
REFERENCE NAME NAME REFERENCE
A5U1-1
A5U1-2
A5U1-3
A5U1-4
A5U1-5
A5U1-6
A5U1-17
A5U1-19
A5U1-20
A5U1-21
A5U1-22
A5U1-23
A5U1-24
A5U1-25
A5U1-26
A5U1-27
A5U1-28
ACCRQ*
ACCGR*
CE*
WE*
DBIN
(nc)
(nc)
D1
D0
CLK
RESET*
VSS
TE
REN
IFC
NDAC
NRFD
(nc)
ACCRQ*
ACCGR*
CD*
WE*
DBIN
D1
D0
CLK
RESET*
VSS
TE
REM
IFC
NDAC
NRFD
(nc)
A5U1-1
A5U1-2
A5U1-3
A5U1-4
A5U1-5
A5U1-6
A5U1-17
A5U1-19
A5U1-20
A5U1-21
A5U1-22
A5U1-23
A5U1-24
A5U1-25
A5U1-26
A5U1-27
A5U1-28