Motorola MVME172 manual Vgto, Time on

2

VMEchip2

DMAC Ton/Toff Timers and VMEbus Global Time-out Control Register

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

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

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