P2 Signal Multiplexing - Motorola MVME2700 Series Installation And Use Manual

VMEP
LANP
SCSIP

P2 Signal Multiplexing

Due to the limited supply of available pins in the P2 backplane connectors
of MVME2700 models that are configured for MVME761 I/O mode,
certain signals are multiplexed through VMEbus connector P2 for
additional I/O capacity.
The signals affected are synchronous I/O control signals that pass between
the base board and the MVME761 transition module. The multiplexing is
a hardware function that is entirely transparent to software.
Four signals are involved in the P2 multiplexing function: MXDO, MXDI,
MXCLK, and MXSYNC .
MXDO is a time-multiplexed data output line from the main board and
MXDI is a time-multiplexed line from the MVME761 module. MXCLK
is a 10MHz bit clock for the MXDO and MXDI data lines. MXSYNC is
asserted for one bit time at time slot 15 (refer to the following table) by the
MVME2700 base board. The MVME761 transition module uses
MXSYNC to synchronize with the base board.
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VMEbus present. If set, there is no VMEbus interface. If
cleared, the VMEbus interface is supported.
Ethernet present. If set, no Ethernet transceiver interface is
installed. If cleared, there is on-board Ethernet support.
SCSI present. If set, there is no on-board SCSI interface. If
cleared, on-board SCSI is supported.
Block Diagram
5
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