Introduction to HS488
Appendix C
GPIB-140 User Manual
C- 6
© National Instruments Corp.
Case 3: Talker Is Not HS488 Capable, But Listener Is HS488
Capable
The Talker does not send an HSC message to the Listener, but begins sourcing bytes by
using the IEEE 488.1 protocol.
The Addressed Listener (HS488 or 488.1) accepts bytes by using the IEEE 488.1
standard three-wire handshake. Refer to Figure C-4.
~ATN
~DIO1-8
(composite)
~DAV
~NDAC
~NRFD
T1
Figure C-4. Talker Is Not HS488 Capable, But Listener Is HS488 Capable
System Configuration
The HS488 Acceptor Handshake and Source Handshake interface functions depend on
several time delays. Some of these delays are a function of the total system cable length.
The Controller must communicate this system configuration data to HS488 devices after
the system powers on. The Controller configures HS488 devices by sourcing two
multiline messages while ATN is true.
The first message is the Configuration Enable (CFE) message. The Controller sends the
CFE message by driving a bit pattern (1E hex) that the IEEE 488.1 standard does not
define on the DIO signal lines. The CFE message enables HS488 devices to interpret the
SCG message that follows. The second message is a Secondary Command Group (SCG)
message that contains the configuration data. The Secondary Command has the bit
pattern 6n hex, where n is the meters of cable in the system. The Secondary Command
Group includes CFG1-CFG15 in Appendix D, Multiline Interface Messages .