Motorola MVME172 User Manual Page 144

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2-66 Computer Group Literature Center Web Site
VMEchip2
2
DMAC Ton/Toff Timers and VMEbus Global Time-out Control Register
This register controls the DMAC time off timer, the DMAC time on timer,
and the VMEbus global time-out timer.
VGTO These bits define the VMEbus global time-out value.
When DS0 or DS1 is asserted on the VMEbus, the timer
begins timing. If the timer times out before the data
strobes are removed, a BERR signal is sent to the
VMEbus. The global time-out timer is disabled when the
VMEchip2 is not system controller.
0 8 µs
1 64 µs
2 256 µs
3 The timer is disabled
TIME ON These bits define the maximum time the DMAC spends
on the VMEbus:
0 16 µs 4 256 µs
1 32 µs 5 512 µs
2 64 µs 6 1024 µs
3 128 µs 7 When done (or no data)
TIME OFF These bits define the minimum time the DMAC spends
off the VMEbus:
0 0 µs 4 128 µs
1 16 µs 5 256 µs
2 32 µs 6 512 µs
3 64 µs 7 1024 µs
ADR/SIZ $FFF4004C (8 bits of 32)
BIT 23 22 21 20 19 18 17 16
NAME TIME OFF TIME ON VGTO
OPER R/W R/W R/W
RESET 0 PS 0 PS 0 PS
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