Processor Board Interfaces; Rs-232 Interface - HP 340 Series Service Manual

Processor Board Interfaces
Overview
The processor board's interfaces meets most, if not all, I/O needs of the Design Automation
marketplace. These interfaces incllude:
• RS-232.
• HP-IB.
• HP-HIL.
To lnaintain software compatibility, the designs of several existing interface accessories used
in other Series 300 computers were integrated together. Interface products emulated on the
processor board are the same as the 98561-66532 Human Interface Card.
Each of these sections of the processor board operates independently from one another. Software
compatibility is assured.
RS-232 Interface
An RS-232 Interface section is part of the processor board's electronics. Using an INS8250
UART, it's almost identical to the HP 98644A RS-232 Serial Interface Card. It differs from the
HP 98644A Interface Card in that it:
• Allows interrupts at level 5 only. There are no switches to change the interrupt level is
the same as the HP 98644 Card.
• Permanently sets the select code to 9.
• Does not allow reconfiguration to change the RS-232's ID to that of the HP 98626 card.
Two switches on the processor board are associated with RS-232. Accessible through the
configuration switch port in the rear panel, they perform the following functions:
• REM -
Controls the local/remote bit in the ID register.
• MEN -
Sets the handshake input lines to their default condition, all ones.
In addition to the registers built into the INS8250 UART, two external register have also been
implemented. Both sets of registers are multi-mapped within a 64 Kbyte region of memory
associated with I/O select code 9.
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Functional Description