The AST Fourport card has one 8 way DIP switch (S1). Holding the card with
the components towards you and the ISA connector at the bottom, S1-1 is on
the left and S1-8 on the right. A switch is on if it is pushed away from
the ISA connector. Most of the rest of this is retyped from the manual.
With S1-1 on the card is in compatible mode (channels 1 and 2 respond as
com1 and com2 under DOS).
S1-2 on (and positions 3 through 7 off) selects irq2 as the interrupt line
for channels 3 and 4. In compatible mode (default), channels 1 and 2
automatically use irq4 and irq3 respectively.
S1-8 on selects the address for channels 3 (2b0-2b7) and 4 (2b8-2be). In
the compatible mode channel 1's address is automatically 3f8-3ff (com1)
and channel 2 is 2f8-2ff (com2).
Non-compatible mode (64KB & 256Kb PC, PC-XT or PC-AT)
S1-1 S1-8 channel 1 channel 2 channel 3 channel 4 vector
off on 2a0-2a7 2a8-2af 2b0-2b7 2b8-2be 2bf
Alternate Non-compatible mode (PC-XT or PC-AT)
S1-1 S1-8 channel 1 channel 2 channel 3 channel 4 vector
off off 1a0-1a7 1a8-1af 1b0-1b7 1b8-1be 1bf
Compatible mode (PC-AT)
S1-1 S1-8 channel 1 channel 2 channel 3 channel 4 vector
on on 3f8-3ff 2f8-2ff 2b0-2b7 2b8-2be 2bf
on off 3f8-3ff 2f8-2ff 1b0-1b7 1b8-1be 1bf
Interrupt settings.
In compatible mode channels 1 and 2 use irq 4 and 3 respectively, the
other two channels share a common interrupt as shown below.
In non-compatible mode all channels share a common interrupt as shown
below:
S1 position on Interrupt line
7 irq7
6 irq6
5 irq5
4 irq4
3 irq3
2 irq2
Note that only one interrupt line can be enabled at a time.
Pin assignments:
DB37 Channel Signal name
pin
1 - Not connected
2 3 Data carrier detect DCD
3 3 signal ground
4 3 clear to send CTS
5 3 receive data RxD
6 4 ring indicator RI
7 4 data terminal ready DTR
8 4 data set ready DSR
9 4 request to send RTS
10 4 transmit data TxD
11 2 data carrier detect DCD
12 2 signal ground
13 2 clear to send CTS
14 2 receive data RxD
15 1 ring indicator RI
16 1 data terminal ready DTR
17 1 data set ready DSR
18 1 request to send RTS
19 1 transmit data TxD
20 3 ring indicator RI
21 3 data terminal ready DTR
22 3 data set ready DSR
23 3 request to send RTS
24 3 transmit data TxD
25 4 data carrier detect DCD
26 4 signal ground
27 4 clear to send CTS
28 4 receive data RxD
29 2 ring indicator RI
30 2 data terminal ready DTR
31 2 data set ready DSR
32 2 request to send RTS
33 2 transmit data TxD
34 1 data carrier detect DCD
35 1 signal ground
36 1 clear to send CTS
37 1 receive data RxD
Chris
terhi.victor@logonet.com