Motorola MVME172 - Manual (Page 137)

LCSR Programming Model
http://www.mcg.mot.com/literature 2-59
2
DMAC Control Register 2 (bits 0-7)
This portion of the control register is loaded by the processor or the DMAC
when it loads the command word from the command packet. Because this
byte is loaded from the command packet in the command chaining mode,
the descriptions here also apply to the control word in the command
packet.
VME AM These bits define the address modifier codes the DMAC
drives on the VMEbus when it is bus master. During
non-block transfer cycles, bits 0-5 define the VMEbus
address modifiers. During block transfers, bits 2-5 define
VMEbus address modifier bits 2-5, and address modifier
bits 0 and 1 are provided by the DMAC to indicate a block
transfer. Block transfer mode should not be set in the
address modifier codes. The special block transfer bits
should be set to enable block transfers. If non-block cycles
are required to reach a 32- or 64-bit boundary, bits 0 and
1 are used during these cycles.
BLK These bits control the block transfer modes of the DMAC:
0 Block transfers disabled
1 The DMAC executes D32 block transfer
cycles on the VMEbus. In the block transfer
mode, the DMAC may execute byte and two-
byte cycles at the beginning and ending of a
transfer in non-block transfer mode. If the
D16 bit is set, the DMAC executes D16 block
transfers.
2 Block transfers disabled
ADR/SIZ $FFF40034 (8 bits of 32)
BIT 7 6 5 4 3 2 1 0
NAME BLK VME AM
OPER R/W R/W
RESET 0 PS 0 PS