Motorola MVME172 manual Adma

Models: MVME172

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4

IP2 Chip

bits in the General Control Registers, these width control bits define the width of both the memory and I/O interface.

 

WIDTH1

WIDTH0

Assumed Data Bus Width

 

 

 

 

 

0

0

32 bits

 

 

 

 

 

0

1

8 bits

 

 

 

 

 

1

0

16 bits

 

 

 

 

 

1

1

Reserved

ADMA

 

 

 

Setting ADMA to a one will enable the address mode

 

DMA operation. Setting it to a zero will enable the

 

standard mode of DMA operation. Refer to the section on

 

the DMA Enable Function for information and

 

restrictions on the operation of the ADMA control bit.

DTBL

DMAC operates in the direct mode when this bit is low,

 

and it operates in the command chaining mode when this

 

bit is high.

 

 

DHALT

When this bit is high, DMA halts at the end of a command

 

when DMA is operating in the command chaining mode.

When this bit is low, DMA executes the next command in the list. Software must be careful not to change the state of bits 0 through 6 of this control register when the DHALT bit is set.

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Page 274
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Motorola MVME172 manual Adma