GP Bus DMA Controller
14-20 Élan™SC520 Microcontroller User’s Manual
14.6.1.2 Configuring a 16-Bit Channel in Normal GP-DMA Mode
In normal GP-DMA mode, there are three 16-bit channels: 5, 6 and 7. Any external request
can be mapped to one of these channels. The internal requests from the UART serial ports
cannot be mapped to a 16-bit channel because they only support 8-bit data transfer. The
following steps configure a 16-bit channel for an external request.
1. Enable the DMA master core.
2. Program the operating frequency if not using the default 4 MHz.
3. Map the external request to a specific channel.
4. Program the memory address, transfer count, page address, and extended page
address of the associated channel.
5. Program DMA mode, type, address increment mode, and priority mode.
6. Unmask the channel request in the Master DMA General Mask (MSTDMAGENMSK)
register (Port 00DEh). At this point, the GP-DMA controller is ready to accept the external
request.
14.6.1.3 Configuring an 8-Bit Channel in Enhanced GP-DMA Mode
In enhanced GP-DMA mode, channels 5, 6, and 7 can be configured to be 8-bit channels.
Any internal request from the UART serial ports can be mapped to Channel 3 for the
enhanced GP-DMA mode features. The 8-bit external devices can be mapped to channels
3, 5, 6, and 7. The following steps configure an 8-bit channel for an external request.
1. Enable the DMA slave core if using Channel 3, otherwise enable the master core.
2. If using Channel 3, program Channel 4 to use cascade mode via the TRNMOD field in
the Master DMA Channel 4–7 Mode (MSTDMAMODE) register (Port 00D6h) and
unmask Channel 4. Also, if using channels 5, 6, or 7, set the corresponding
CHx_ALT_SIZE bit in the GP-DMA Control (GPDMACTL) register (MMCR offset D80h).
3. Program the operating frequency if not using the default 4 MHz.
4. Enable enhanced GP-DMA mode.
5. Map the external request to a specific channel.
6. Program the memory address, transfer count, page address, and extended page
address of the associated channel.
7. Program the extended transfer count for any transfer larger than 64 Kbytes (optional).
8. Program DMA mode, type, address increment mode, and priority mode.
9. Program the next address, next transfer count, and enable buffer chaining mode
(optional).
10.Unmask the channel request in the General Mask register. At this point, the GP-DMA
controller is ready to accept the external request.
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