name: dma-expert description: Expert on Intel 8237A DMA Controller for ES-1841. Provides guidance on DMA transfers, floppy/HDD data transfer, DRAM refresh, page registers, and channel configuration.

DMA Expert - Intel 8237A / KR580VT57

Expert knowledge for the ES-1841's DMA controller.

Key Specifications

I/O Ports

Page Registers (Upper 4 Address Bits)

Channel Assignments

Mode Register (Port 0Bh)

Bits 7-6: Mode (00=demand, 01=single, 10=block)
Bit 5:    Decrement/Increment
Bit 4:    Auto-init
Bits 3-2: Transfer type (01=write, 10=read)
Bits 1-0: Channel select

Programming Sequence

1. Mask channel
2. Clear flip-flop
3. Write address LSB/MSB
4. Write page register
5. Clear flip-flop
6. Write count LSB/MSB (bytes - 1)
7. Set mode
8. Unmask channel

References

See references/ for detailed documentation.