Alpha Microsystems AM-990 Service-Handbuch - Seite 13

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SBC AM-140 CPU BOARD

The AM-140 is a 50Mhz main logic board available for the SBC. Most of the AM-140
specifications are covered in Appendix A (in the SBC owner's manual); however, the
following list highlights some of the key features on the AM-140 board:
Memory expansion up to 64 megabytes.
I/O expansion up to 66 serial ports.
On-board intelligent ESDI controller.
68030 Processor chip.
The sections that follow include information on user configurable options for the AM-140
board.
Most of the jumpers on the AM-140 board are factory configured and should not be
moved. Only the features discussed in the next sections have jumpers that are user
configurable.

Remote Reset Capability

As discussed in Appendix B in the owner's manual, it is possible to reset the SBC
remotely through serial I/O Port "0." If properly configured, you can use a push button
switch to short Pin 1 in that connector to Pin 7 (Signal Ground), resetting the computer.
To enable remote reset, you must install a shorting block in the REMOTE RESET
position on the SBC main logic board. See the illustration.

Serial I/O Port Configuration

Ports 0 and 1 on the SBC are factory configured for RS-232 compatibility. You can
configure either or both of these ports for RS-422 compatibility if desired. For each port,
three jumpers on the main logic board control whether it is set for RS-232 or RS-422
compatibility. You must set all three to either 232 or 422. For Port 0, the jumpers are
W2, W3 and W4; for Port 1, they are W5, W6 and W7.

Configuring SBC Memory

Installing memory boards in the SBC couldn't be easier. There are no jumpers to
configure, no switches to set, and no concerns with beginning or ending memory
addresses.
There are four connectors designed for SBC memory boards; J12, J13, J14, and J15.
The first memory board is installed in J12; the second memory board is installed in J13;
the third goes in J14; and the fourth goes in J15.
AM-990 SBC Computer Service Manual
DSS-10524-00, Rev. A01