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Appendix B
Introduction to HS488
Same Cabling Restrictions as IEEE 488.1
Systems that meet the IEEE 488.1 requirements for high-speed operation also meet the HS488
requirements. HS488 cabling requirements are also the same as the requirements in the
IEEE 488.1 standard.
However, using HS488 does not reduce software overhead. Also, system throughput increases
depend on data block size.
IEEE 488.1 Requirements for High-Speed
Operation (T1 Delay
≥
350 ns)
The IEEE 488.1 standard requires that devices used in high-speed operation must use three-state,
48 mA drivers on most signals. Each device must add no more than 50 pF capacitance on each
signal, and all devices must be powered on.
The total cable length in a system must be no more than 15 m, or 1 m times the number of devices
in the system.
HS488 System Requirements
An HS488 system must meet the IEEE 488.1 requirements and it must implement the following
three new interface functions:
•
Talking devices must use the
Source Handshake Extended (SHE)
interface function, which
is an extension of the IEEE 488.1 SH function.
•
Listening devices must use the
Acceptor Handshake Extended (AHE)
interface function,
which is an extension of the IEEE 488.1 AH function. Accepting devices must have a
buffer of at least 3 bytes to store received data.
•
HS488 devices must implement the
Configuration (CF)
interface function. At system
power on, the Controller uses previously undefined multiline messages to configure HS488
devices. The CF function enables devices to interpret these multiline messages.
