1.Data bus with 8 lines D0 to D7
The transmission is bit-parallel and byte-serial in the ASCII/ISO code. D0 is the least significant bit, D7 the most significant bit.
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 messages.
SRQ (Service Request),
active LOW enables the connected device to send a service request to the controller.
REN (Remote Enable),
active LOW permits switchover to remote control.
EOI (End or Identify),
has two functions in connection with ATN:
| ATN=HIGH | active LOW marks the end of data transmission. |
| ATN=LOW | active LOW triggers a parallel poll. |
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 connected devices is not ready for data transfer.
NDAC (Not Data Accepted),
active LOW signals that the instrument connected is accepting the data on the data bus.