LCSR Programming Model

 

 

A32

When this bit is high, the first map decoder responds to

 

VMEbus A32 (extended) access cycles. When this bit is

 

low, the first map decoder does not respond to VMEbus

 

A32 access cycles.

USR

When this bit is high, the first map decoder responds to

 

VMEbus user (non-privileged) access cycles. When this

 

bit is low, the first map decoder does not respond to

 

VMEbus user access cycles.

SUP

When this bit is high, the first map decoder responds to

 

VMEbus supervisory access cycles. When this bit is low,

 

the first map decoder does not respond to VMEbus

 

supervisory access cycles.

2

Programming the Local Bus to VMEbus Map Decoders

This section includes programming information on the local bus to

VMEbus map decoders and the GCSR base address registers.

The local bus to VMEbus interface allows onboard local bus masters access to off-board VMEbus resources. The address of the VMEbus resources as viewed from the local bus is controlled by the local bus slave map decoders, which are part of the local bus to VMEbus interface. Four of the six local bus to VMEbus map decoders are programmable, while the two I/O map decoders are fixed. The first I/O map decoder provides an A16/D16 or A16/D32 space at $FFFF0000 to $FFFFFFFF which is the VMEbus short I/O space. The second I/O map decoder provides an A24/D16 space at $F000000 to $F0FFFFFF and an A32/D16 space at $F1000000 to $FF7FFFFF.

A programmable segment may vary in size from 64KB to 4GB in increments of 64KB. Address translation for the fourth segment is provided by the address translation registers which allow the upper 16 bits of the VMEbus address to be provided by the address translation address register rather than the upper 16 bits of the local bus.

http://www.mcg.mot.com/literature

2-37

Page 115
Image 115
Motorola MVME172 manual Programming the Local Bus to VMEbus Map Decoders, A32 access cycles