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4-18 361834-002 Technical Reference Guide
System Support
The remaining address lines are in an undefined state during the refresh cycle. The refresh
operations are driven by a 69.799-KHz clock generated by Interval Timer 1, Counter 1. The
refresh rate is 128 refresh cycles in 2.038 ms.
DMA Controller Registers
Table 4-11 lists the DMA Controller Registers and their I/O port addresses. Note that there is a
set of registers for each DMA controller.
Table 4-11.
DMA Controller Registers
Register Controller 1 Controller 2 R/W
Status 008h 0D0h R
Command 008h 0D0h W
Mode 00Bh 0D6h W
Write Single Mask Bit 00Ah 0D4h W
Write All Mask Bits 00Fh 0DEh W
Software DRQx Request 009h 0D2h W
Base and Current Address—Ch 0 000h 0C0h W
Current Address—Ch 0 000h 0C0h R
Base and Current Word Count—Ch 0 001h 0C2h W
Current Word Count—Ch 0 001h 0C2h R
Base and Current Address—Ch 1 002h 0C4h W
Current Address—Ch 1 002h 0C4h R
Base and Current Word Count—Ch 1 003h 0C6h W
Current Word Count—Ch 1 003h 0C6h R
Base and Current Address—Ch 2 004h 0C8h W
Current Address—Ch 2 004h 0C8h R
Base and Current Word Count—Ch 2 005h 0CAh W
Current Word Count—Ch 2 005h 0CAh R
Base and Current Address—Ch 3 006h 0CCh W
Current Address—Ch 3 006h 0CCh R
Base and Current Word Count—Ch 3 007h 0CEh W
Current Word Count—Ch 3 007h 0CEh R
Temporary (Command) 00Dh 0DAh R
Reset Pointer Flip-Flop (Command) 00Ch 0D8h W
Master Reset (Command) 00Dh 0DAh W
Reset Mask Register (Command) 00Eh 0DCh W