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- Path: sparky!uunet!spool.mu.edu!mixcom.com!ttyytt
- From: ttyytt@mixcom.com (Adam Costello)
- Newsgroups: comp.sys.amiga.hardware
- Subject: Re: null-modem-cable : how to make ?
- Message-ID: <1992Aug14.015501.26564@mixcom.com>
- Date: 14 Aug 92 01:55:01 GMT
- Article-I.D.: mixcom.1992Aug14.015501.26564
- References: <1992Aug13.142254.22660@sun1.ruf.uni-freiburg.de> <1992Aug13.183859.4170@fripp.ri.cadre.com>
- Organization: Milwaukee Internet Xchange BBS, Milwaukee, WI U.S.A.
- Lines: 63
-
- In article <1992Aug13.183859.4170@fripp.ri.cadre.com> jh@cadre.com writes:
- >You should be able to get away with connecting pins 7 and 20 straight through
- >and crossing pins 2 and 3. That's bare bones, but it should do it. If you've
- >got an 8 wire cable to work with, connect 4,5,6,7,8 and 20 straight through,
- >and cross 2 and 3.
-
- No! Pins 4 and 20 (on data terminal equipment) are RTS and DTR. These are
- outputs! You never want to connect two outputs together. There's
- probably protection built into the serial ports, but better safe than sorry.
-
- There are two wirings for null-modems I would recommend, depending on
- whether RTS/CTS are being used for their original intended purpose (to keep
- the terminal from sending data when the modem isn't ready for it), or for
- flow control in both directions.
-
- Original intention
- ------------------
-
- shield 1 --------- 1 shield
-
- TXD 2 ---\ /--- 2 TXD
- X
- RXD 3 ---/ \--- 3 RXD
-
- RTS 4 -+ +- 4 RTS
- | |
- CTS 5 -+ +- 5 CTS
-
- RLSD 8 -+ +- 8 RLSD
- | |
- DSR 6 -+-\ /-+- 6 DSR
- X
- DTR 20 ---/ \--- 20 DTR
-
- SGND 7 --------- 7 SGND
-
-
- Flow Control
- ------------
-
- shield 1 --------- 1 shield
-
- TXD 2 ---\ /--- 2 TXD
- X
- RXD 3 ---/ \--- 3 RXD
-
- RTS 4 ---\ /--- 4 RTS
- X
- CTS 5 ---/ \--- 5 CTS
-
- RLSD 8 -+ +- 8 RLSD
- | |
- DSR 6 -+-\ /-+- 6 DSR
- X
- DTR 20 ---/ \--- 20 DTR
-
- SGND 7 --------- 7 SGND
-
-
- The only difference between the two is with RTS/CTS. Note that RLSD
- (Receive Line Signal Detector) is also know as CD (Carrier Detect).
-
- AMC
-