Tektronix CMD 80, User Manual

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Appendix D: Remote Control
D–2
CMD 80 Digital Radiocommunication Tester User Manual
The bus connections are in accordance with the IEEE 488 standard. The interface
contains three groups of bus lines as follows:
H
Data bus with 8 lines DIO 1 to DIO 8
Data transmission is bit-parallel and byte-serial with the characters in ISO
7-bit code (ASCII code).
DIO 1 represents the least significant bit and DIO 8 the most significant bit.
H
Control bus with 5 lines
This is used to transmit control functions as follows:
ATN (Attention) – becomes active low when addresses, universal com-
mands, or addressed commands are transmitted to the connected device.
REN (Remote Enable) – enables the device to be switched to the remote
status.
SRQ (Service Request) – enables a connected device to send a Service
Request to the controller by activating this line.
IFC (Interface Clear) – is activated by the controller to set the interface to a
defined status.
EOI (End or Identify) – is used to identify the end of data transfer and is
used with a parallel poll.
H
Handshake bus with 3 lines
This is used to control the data transfer timing as follows:
NRFD (Not Ready For Data) – an active low on this line signals to the
talker/controller that one of the connected devices is not ready to accept data.
DAV (Data Valid) – is activated by the talker/controller shortly after a new
data byte has been applied to the data bus.
NDAC (Not Data Accepted) – is held at active low by the connected device
until it has accepted the data present on the data bus.
Detailed information on the data transfer timing is available in the IEC 625-1
standard.
According to the IEC 625-1 standard, devices controlled by means of the GPIB
bus can be equipped with different interface functions. Table D–1 lists the
interface functions applicable to the tester.