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Programmable Hardware Manual (PHM)
© Tibbo Technology Inc.
example, our own "serial-over-IP" application supports these lines. Again, instead of
using TX3 and RX3 (pins 4 and 6) as the lines of an independent serial channel, it is
possible to use them as DTR and DSR lines, as is common.
To simplify the discussion, let's look at the RS232 port from the serial-over-IP
application's point of view. This application defines 15 mapping options:
Mappi
ng
optio
n
Available signals
Pins on the DB9M connector
Miss
ing
line
#
2
#3
#8
#7
#6
#4
#1
Optio
n 0
RX/TX/CTS/RTS/DS
R/DTR
RX
TX
CT
S
RT
S
DS
R
DT
R
---
---
Optio
n 1
RX/TX/CTS/RTS/DS
R/DTR + RX/
tx
RX
TX
CT
S
RT
S
DS
R
DT
R
RX4
tx4
Optio
n 2
RX/TX/CTS/RTS +
RX/TX + RX/
tx
RX
TX
CT
S
RT
S
RX3
TX
3
RX4
tx4
Optio
n 3
RX/TX/CTS/RTS +
RX/TX/CTS/
rts
RX
TX
CT
S
RT
S
RX3
TX
3
CT
S3
rts3
Optio
n 4
RX/TX/CTS/RTS +
RX/TX/DSR/
dtr
RX
TX
CT
S
RT
S
RX3
TX
3
DS
R3
dtr3
Optio
n 5
RX/TX/DSR/DTR +
RX/TX + RX/
tx
RX
TX
RX2
TX
2
DS
R
DT
R
RX4
tx4
Optio
n 6
RX/TX/DSR/DTR +
RX/TX/CTS/
rts
RX
TX
RX2
TX
2
DS
R
DT
R
CT
S2
rts2
Optio
n 7
RX/TX/DSR/DTR +
RX/TX/DSR/
dtr
RX
TX
RX2
TX
2
DS
R
DT
R
DS
R2
dtr2
Optio
n 8
RX/TX + RX/TX +
RX/TX + RX/
tx
RX
TX
RX2
TX
2
RX3
TX
3
RX4
tx4
Optio
n 9
RX/TX/CTS/
rts
+
RX/TX + RX/TX
RX
TX
RX2
TX
2
RX3
TX
3
CT
S
rts
Optio
n 10
RX/TX/DSR/
dtr
+
RX/TX + RX/TX
RX
TX
RX2
TX
2
RX3
TX
3
DS
R
dtr
Optio
n 11
RX/TX/CTS/RTS +
RX/
tx
/CTS/RTS
RX
TX
CT
S
RT
S
CT
S4
RT
S4
RX4
tx4
Optio
n 12
RX/TX/CTS/RTS +
RX/
tx
/DSR/DTR
RX
TX
CT
S
RT
S
DS
R4
DT
R4
RX4
tx4
Optio
n 13
RX/TX/DSR/DTR +
RX/
tx
/CTS/RTS
RX
TX
CT
S4
RT
S4
DS
R
DT
R
RX4
tx4
Optio
n 14
RX/TX/DSR/DTR +
RX/
tx
/DSR/DTR
RX
TX
DS
R4
DT
R4
DS
R
DT
R
RX4
tx4
"Available signals" column shows a particular combination of I/O lines for each
option. For example, option 0 defines the standard serial port arrangement with RX,
TX, CTS, RTS, DSR, and DTR lines. Option 2 gives you one channel with RX, TX,
CTS, and RTS lines, one more channel with just RX and TX lines, and yet another
channel with a single RX line. The TX line is "missing" because, once again, there are
only three outputs available. This is why this line is shown in gray (
tx
).