Motorola MVME172 manual Vme Am

Models: MVME172

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LCSR Programming Model

DMAC Control Register 2 (bits 0-7)

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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

2

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Page 137
Image 137
Motorola MVME172 manual Vme Am