Motorola MC68340 manual Freescale Semiconductor, Inc

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

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

6.9.1.1DMA 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.

6.9.1.2DMA 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).

MOTOROLAMC68340 USER’S MANUAL6- 37

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