MC68340 datasheet(287/441 Pages) FREESCALE

287 / 441 page

MOTOROLA

MC68340 USER’S MANUAL

6- 37

• Select the direction of transfer if in single-address mode (ECO bit), or select which

device generates requests if in dual-address mode.

6.9.1.1 DMA CHANNEL OPERATION IN SINGLE-ADDRESS MODE. The following steps

are required to begin a DMA transfer in single-address mode.

Channel Control Register (CCR)

• Write a zero to the start bit (STR) to prevent the channel from starting the transfer

prematurely.

• Select the amount by which to increment the source address for a read cycle (SAPI

bit) or the destination address for a write cycle (DAPI bit).

• Define the transfer size by selecting the source size for a read cycle (SSIZE field) or

by selecting the destination size for a write cycle (DSIZE field).

• Select external burst request mode or external cycle steal request mode (REQ field).

• Set the S/D bit for signal-address transfer.

Channel Status Register (CSR)

• Clear the CSR by writing $7C into it. The DMA cannot be started until the DONE, BES,

BED, CONF, and BRKP bits are cleared.

Function Code Register (FCR)

• Encode the source function code for a read cycle or the destination function code for a

write cycle.

Address Register (SAR or DAR)

• Write the source address for a read cycle or the destination address for a write cycle.

Byte Transfer Counter (BTC)

• Encode the number of bytes to be transferred.

Channel Control Register (CCR)

• Write a one to the start bit (STR) to allow the transfer to begin.

6.9.1.2 DMA CHANNEL OPERATION IN DUAL-ADDRESS MODE. The following steps

are required to begin a DMA transfer in dual-address mode.

Channel Control Register (CCR)

• Write a zero to the start bit (STR) to prevent the channel from starting the transfer

prematurely.

• Select the amount by which to increment the source and destination addresses (SAPI

and DAPI bits).

• Select the source and destination sizes (SSIZE and DSIZE fields).

• Select internal request, external burst request mode, or external cycle steal request

mode (REQ field).

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

MC68340 Datasheet(PDF) 287 Page - Freescale Semiconductor, Inc