Compaq W4000 Manual De Usuario
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
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
4.4.2.2
trolle
gi
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.
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, S
A
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.
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