Chapter 4 System Support
DMA controller 1 can move up to 64 Kbytes of data per DMA transfer. DMA controller 2 can
move up to 64 Kwords (128 Kbytes) of data per DMA transfer. Word DMA operations are only
ipherals.
A18,19 are driven low.
e. The refresh
ounter 1. The
T 2 lists the DMA tro port addresses. Note that there is a set
of registers for each DMA controller.
possible between 16-bit memory and 16-bit per
The RAM refresh is designed to perform a memory read cycle on each of the 512 row addresses
in the DRAM memory space. Refresh operations are used to refresh memory on the 32-bit
memory bus and the ISA bus. The refresh address is provided on lines SA00 through SA08.
ddress lines LA23..17, SA
ate during the refresh cycl
erations are driven by a 69.799-KHz clock generated by Interval Timer 1, C
The remaining address lines are in an undefined st
op
refresh rate is 128 refresh cycles in 2.038 ms.
DMA Con r Re sters able 4-1 Con ller Registers and their I/O
Table 4-12. DMA Controller Registers
Table 4-12.
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
Compaq Evo and Workstation Personal Computers
Featuring the Intel Pentium 4 Processor
Second Edition – January 2003
4-22