DEC Digital Alpha VME 4/224 User Manual page 269

Bit 0 Set to include VMEbus acquisition time in local bus timeout.
Bit 1 When VME interface is used as system controller, this bit is set to
indicate arbitration timeout.
Bits 4-2 Recommended timeout period for local bus is 64 µs (011).
Bits 7-5 Recommended timeout period for VMEbus is 128 µs (100).
The use of timeout periods depends on the VME environment. When
the Digital Alpha VME 4 system is a system controller and a cycle
times out on the local bus after timing out on the VMEbus, the cycle
hangs. To avoid this condition, set the timeout period for the local bus
first or not at all.
LBTR
Bits 3-0 Minimum PAS assertion time. Keep the default of zero.
Bit 4 Minimum DS deasserted time. Must be set in the Digital Alpha VME
4 system.
Bits 7-5 Minimum PAS deasserted time. Must be binary 110.
BTDR
Bit 0 Dual Path enable. Must be set.
Bit 1 AMSR register. Sets up user-defined address modifier codes for block
mode transfers.
Bit 2 Local bus 256 bus byte boundary. Recommend this be set.
Bit 3 VME 256 bus crossing enabled. Recommend this be set.
Bit 4 Enables D64 master operation.
Bit 5 Enable enhanced turbo mode. Must be clear.
Bit 6 Enables D64 slave operation. Recommend this be set.
Bit 7 Enable 2 KB boundary crossing for D64. If set, software must check
that the D64 block mode transfer start address is 2 KB aligned and
that the transfer does not cross a 64 KB boundary.
ICR
Bit 0 Read-only system controller pin.
Bit 1 Turbo enable. Must be clear.
Bit 2 Metastability delay. Recommend this be clear.
Bits 4,3 Deadlock signaling. Must be clear.
Bits 5-7 RMC Control bits 1 to 3.
ARCR
Bits 3-0 VMEbus fairness timer enable.
Bit 4 DRAM refresh enable. Must be clear.
VME Interface 10–35