Lakeshore Learning Materials 642 - Manual (Page 53)

Lake Shore Model 642 Electromagnet Power Supply User’s Manual
Computer Interface Operation 5-1
CHAPTER 5
COMPUTER INTERFACE OPERATION
5.0 GENERAL
This chapter provides operational instructions for the computer interface for the Lake Shore Model 642 Electromagnet
Power Supply. Either of the two computer interfaces provided with the Model 642 permit remote operation. The first is
the IEEE-488 Interface described in Paragraph 5.1. The second is the Serial Interface described in Paragraph 5.2. The
two interfaces share a common set of commands detailed in Paragraph 5.3. Only one interface can be used at a time.
5.1 IEEE-488 INTERFACE
The IEEE-488 Interface is an instrumentation bus with hardware and programming standards that simplify instrument
interfacing. The Model 642 IEEE-488 Interface complies with the IEEE-488.2-1987 standard and incorporates its
functional, electrical, and mechanical specifications unless otherwise specified in this manual.
All instruments on the interface bus perform one or more of the interface functions of TALKER, LISTENER, or BUS
CONTROLLER. A TALKER transmits data onto the bus to other devices. A LISTENER receives data from other
devices through the bus. The BUS CONTROLLER designates to the devices on the bus which function to perform.
The Model 642 performs the functions of TALKER and LISTENER but cannot be a BUS CONTROLLER. The BUS
CONTROLLER is the digital computer which tells the Model 642 which functions to perform.
Below are Model 642 IEEE-488 interface capabilities:
• SH1: Source handshake capability.
• RL1: Complete remote/local capability.
• DC1: Full device clear capability.
• DT0:
No device trigger capability.
• C0: No system controller capability.
• T5: Basic TALKER, serial poll capability, talk only, unaddressed to talk if addressed to listen.
• L4: Basic LISTENER, unaddressed to listen if addressed to talk.
• SR1: Service request capability.
• AH1: Acceptor handshake capability.
• PP0:
No parallel poll capability.
• E1: Open collector electronics.
Instruments are connected to the IEEE-488 bus by a 24-conductor connector cable as specified by the standard. Refer to
Paragraph 7.12.2. Cables can be purchased from Lake Shore or other electronic suppliers.
Cable lengths are limited to 2 meters for each device and 20 meters for the entire bus. The Model 642 can drive a bus
with up to 10 loads. If more instruments or cable length is required, a bus expander must be used.