6. DMA Controller
46
connections internal to the 386 EX. Note that the synchronous serial channel is not
implemented on the ZT 8904 in favor of providing an additional asynchronous serial
channel.
Channel 0 supports the following devices as DRQ sources (DMACFG.6-4).
•
External DMA slave request
•
COM1 receive buffer full
•
COM2 transmit buffer empty
•
Timer/Counter unit 1 OUT1
Channel 1 supports the following devices as DRQ sources (DMACFG.2-0).
•
Local floppy disk (PC87303 internal floppy controller)
•
Local IEEE-1284 (PC87303 internal parallel port)
•
COM2 receive buffer full
•
COM1 transmit buffer empty
•
Counter/Timer unit 2 OUT2
DMA Configuration
Register
DMA Configuration
Register
DMA Channel 0
DREQ0
DACK0
DMA Channel 1
DREQ1
DACK1
DACK0#
(pin mux)
EOP#
(pin mux)
DACK1#
(pin mux)
S
y
s
t
e
m
B
u
s
DRQ0
Com1 Receiver
Com2 Transmitter
SSIO Transmitter
TCU Counter 1
DRQ1
Com2 Receiver
Com1 Transmitter
SSIO Receiver
TCU Counter 2
386 EX Internal DMA Controller Connections