B-6
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Appendix B
Introduction to HS488
Case 3: Talker Is Not HS488-Capable, But Listener Is
HS488-Capable
The Talker does
not
send an HSC message to the Listener, but sources bytes using the
IEEE 488.1 protocol.
The addressed Listener (HS488 or IEEE 488.1) accepts bytes using the IEEE 488.1 standard
three-wire handshake, as shown in Figure B-5.
Figure B-5.
Listener Is HS488-Capable
System Configuration
The HS488 AHE and SHE 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 the following
two multiline messages while ATN is true:
•
Configuration Enable (CFE)
—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.
•
Secondary Command Group (SCG)
—This message contains the configuration data. The
Secondary Command has the bit pattern 6
n
hex, where
n
is the meters of cable in the
system. The SCG includes CFG1-CFG15 in Appendix C,
Multiline Interface Messages
.
~ATN
~DIO1
8
(compo
s
ite)
~DAV
~NFRD
~NDAC
T1
