AMD Elan SC520 - Configuring a 16-Bit Channel in Enhanced GP-DMA Mode

GP Bus DMA Controller
Élan™SC520 Microcontroller User’s Manual 14-21
14.6.1.4 Configuring a 16-Bit Channel in Enhanced GP-DMA Mode
In enhanced GP-DMA mode, Channel 3 can be configured to be a 16-bit channel. The
16-bit external devices can be mapped to channel 3, 5, 6, and 7. The following steps
configure a 16-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, set the CH3_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 128 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.