Interface Cables - HP 9000 Series 310 Service Information Manual

Microprocessor
The HP-HIL microprocessor on the computer's assembly provides support for link protocol and
is responsible for:
• Configuring the link.
• Processing input device data.
• Error recovery.
• Initiating commands onto the link through the Link Interface.
Link Interface
Data is exchanged between the device and the host computer through the link interface. It
accepts conlmands from the microprocessor for transmitting and receiving messages in an HP-
HIL frame format.
Each frame is a 150 J1sec long, 15-bit fixed format. A frame is shown in Figure 3-6.
idle start
state bit
+ +
command
bit
+
I I
address
L'
opcode/data byte
L1211 1 0 _
L
16151413121
+/-
05%
parity idle
bit state
+
+
1
1
0
IJ
t
stop
bit
1
f.-
~~r u~~,c
-
----~
1
Frome
(150
uSec) - - - - - - . ,
Figure 3-6. HP-HIL Frame Structure
Frames may be sent up to once each 154 sec allowing data transfer rates of up to 6500
bytes/second. HP-HIL protocol perfornls automatic configuration, identification, and polling
of up to seven devices. Error recovery, device and system reset, and simple output commands
provide a simple device integration.
When the computer is turned on, the link is polled for devices. Each device on the link has
its own ID which is sent to the computer and stored in memory. The link is polled 60 times
per second. Should a device have data to input to the computer, it sends its data frame to the
computer for processing. As each device's franles has its own address in a 3-bit word, no more
than 7 devices can be used on the link at one time.
Interface Cables
A four-wire cable connects HP-HIL devices to each other and to the computer. AMP Shielded
Data Link (SDL) connectors are used and are easily installed and removed fronl the computer
or device. Keyboard cable connectors are keyed and are marked with dots to indicate where
they are connected. Figure 3-7 shows the connector pinouts.
50
Functional Description