IEC/IEEE Bus Interface SME
1038.6002.02 6A.2 E-12
2. Control bus with 5 lines.
IFC (Interface Clear),
active low resets the interfaces of the instruments connected to the default setting.
ATN (Attention),
active low signals the transmission of interface messages
inactive high signals the transmission of device-dependent messages.
SRQ (Service Request),
active low enables a device connected to send a service request to the controller.
REN (Remote Enable),
active low permits the switchover to remote control.
EOI (End or Identify),
has two functions in connection with ATN:
active low marks the end of data transmission with ATN=high
active low triggers a parallel poll with ATN=low.
3. Handshake bus with three lines.
DAV (Data Valid),
active low signals a valid data byte on the data bus.
NRFD (Not Ready For Data),
active low signals that one of the device connected is not ready for data transfer.
NDAC (Not Data Accepted),
active low as long as the instrument connected is accepting the data present on the data bus.
Interface Functions
Instruments which can be remote-controlled via IEC bus can be equipped with different interface
functions. Table A-1 lists the interface functions appropriate for the instrument.
Table A- 1 Interface function
Control
character
Interface function
SH1 Handshake source function (source handshake)
AH1 Handshake drain function (acceptor handshake)
L4 Listener function.
T6 Talker function, ability to respond to serial poll
SR1 Service request function (Service Request)
PP1 Parallel poll function
RL1 Remote/Local switchover function
DC1 Resetting function (Device Clear)
DT1 Trigger function (Device Trigger)
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