Technical data

Theory of Operation 3-17
3.2.5 802.5 Network Controller-AT
The 802.5 Network Controller-AT manages the system’s interface to the IEEE standard
802.5 network. The controller has the following features:
• Full compliance with IEEE 802.5 standards.
• Texas Instrument TMS380 chip set.
• 16 KB of on-board memory.
• Ability to operate with a variety of 802.5 Multistation Access Units (MAUs).
• 9-pin, D-shell, subminiature female connector to support Type 1 and 2 cables,
and an RJ11 phone jack to support Type 3 cables.
• On-board, jumper-selectable address and interrupt level selection.
3.2.6 HP-IB Controller
The optional Hewlett-Packard Interface Bus (HP-IB) is HP’s version of the IEEE 488
interface standard. HP-IB uses a separate board connected to the CPU board by a rib
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bon cable. A mounting plate secures the board to the system unit’s back panel.
The HP-IB board uses a TMS9914 HP-IB controller which allows data transfer rates
up to 450 KB/second. The TMS9914 is a memory-mapped I/O device which is mul-
tiple-mapped within a 64 KB internal I/O device.
One configuration function for the HP-IB system controller is part of the Boot ROM’s
interface configuration mode. When two or more HP-IB devices capable of control-
ling the interface are connected to the interface, one must be configured as the system
controller. The function is set to *yes’ if the system unit is the system controller or ‘no’
if the other device is the system controller.
3.2.7 I/O Boards for Model 400s Systems
The following backplanes support DIO II and ISA option boards.
DIO-II to ISA Converter Board
This board converts 32-bit DIO-II information to 16-bit ISA information while inter
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facing with the DIO-II bus on the motherboard. A connector on the converter board
accepts the AT-compatible backplane.
AT-Compatible Backplane Board
This 4-slot backplane accepts 16-bit ISA PC-AT compatible boards. Although con-