XBusDoc.tioga
Gasbarro, December 13, 1985 4:38:10 pm PST
Last Edited by: Gasbarro April 25, 1986 9:28:08 am PST
XBus
CEDAR 6.0 — FOR INTERNAL XEROX USE ONLY
XBus
Jim Gasbarro
© Copyright 1985 Xerox Corporation. All rights reserved.
Abstract: This interface is a driver for the Busmaster card. It is connected via the XBus expansion port to a DandeTiger. Such a system allows direct control of Multibus peripherals from Cedar.
Created by: Jim Gasbarro
Maintained by: Jim <Gasbarro.pa>
Keywords: Multibus, Busmaster, DandeTiger
XEROX   Xerox Corporation
    Palo Alto Research Center
    3333 Coyote Hill Road
    Palo Alto, California 94304

For Internal Xerox Use Only
1. Jumper Configurations
To use the Busmaster board in the single-master Multibus configuration ensure that these jumpers are installed on the board:
E1, E4, E5, E7, E9, E10, E15, E17, E19, E21, E23, E24
To use the Busmaster board in the PC configuration ensure that these jumpers are installed on the board:
E1, E4, E7, E9, E10, E21, E23, E25
2. Bus Control
The XBus interface provides four basic bus operations:
IORead - performs a I/O read command (IORC).
IOWrite - performs a I/O write command (IOWC).
MemRead - performs a memory read command (MRDC).
MemWrite - performs a memory write command (MWTC).
These opeations can either be performed either on the IBM-PC port or the Multibus port. The global boolean "pcMode" selects the IBM-PC port when TRUE and the Multibus port when FALSE. The jumper configuation must agree with the port being used.
3. Refresh
Many IBM-PC interface cards rely on the PC baseboard to refresh their interal circuitry. A standard IBM-PC expansion chasis does not provide this facility, so the Busmaster card has on-board logic to emulate PC refresh. It is necessary however to initalize this logic to get refresh running. A single call to XBus.PCRefreshOn[] will perform the necessary initialization.