Motorola MVME177, Installation And Use Manual

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MVME177 Functional Description
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4
The EPROMs/Flashes are mapped to local bus address 0 following
a local bus reset. This allows the MC68060 to access the reset vector
and execution address following a reset. The EPROMs are
controlled by the VMEchip2. The following items are all
programmable:
❏
Map decoder
❏
Access time
❏
Time they appear at address 0
For more detail, refer to the VMEchip2 in the Single Board Computers
Programmer's Reference Guide .
SRAM
The boards include 128KB of 32-bit wide static RAM arrays that are
not parity protected and support:
❏
8 bit
❏
16 bit, and
❏
32 bit wide accesses
The SRAM allows the debugger to operate and limited diagnostics
to be executed without the DRAM mezzanine. The SRAM will not
support burst cycles. The SRAM is controlled by the VMEchip2,
and the access time is programmable. Refer to the VMEchip2 in the
Single Board Computers Programmer's Reference Guide for more detail.
The boards are populated with 100 ns SRAMs.
SRAM battery backup is optionally available on the MVME177. The
battery backup function is provided by a Dallas DS1210S. Only one
backup power source is supported on the MVME177. The battery
supplies VCC to the SRAMs when main power is removed.
Each time the MVME177 is powered up, the DS1210S checks the
power source. If the voltage of the backup source is less than two
volts, the second memory cycle is blocked. This allows software to