Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!daver!bungi.com!news From: stacey@guug.de Newsgroups: comp.sys.nsc.32k Subject: Gatewayed mail message Message-ID: <9104041201.AA01629@guug.guug.de> Date: 4 Apr 91 12:01:45 GMT Sender: news@daver.bungi.com Lines: 64 Approved: news@daver.bungi.com To: pc532@daver.bungi.com Subject: PC532 RS232/V24 Serial Ports are DTE, (DCE is normal for a host). From: stacey@guug.de (Julian Stacey) You could skip this article if: - Your PC532 is already serially communicating & - You are not interested in DTE/DCE configuration & - You are not interested in IDC header pin layout for serial ports on the PC532 or new add-on PCBs. The PC532 breaches normal convention, it should have been configured DCE ! To quote the PC532 Functional Spec. Rev. 1.04 11/14/90 Page 4 Line 9: > Each serial channel connects to a 10 pin header which may be connected > (via a transition connector and cable) 1:1 to a DB9 connector > (IBM PC/AT pin compatible). This means: - PC532 Serial Ports connected from the 10 pin IDC header by ribbon to 9 pin IDC D connectors have a DTE configuration, just like a PC-AT, but unlike normal multiple serial port host computers. - You can't just connect the ribbon to a terminal (or PC-AT with terminal emulator) and start debugging your new PC532, abnormally for connecting a computer to a terminal, you need to add a crossover cable (= `null modem'). To Rewire the PC532 from DTE to DCE: Split the ribbons at the D ends, & change to solder type 9 or 25 pin D cons. 10 PIN IDC UART RS232/V24 9 PIN D 25 PIN D PCB HEADER SIGNAL SIGNAL NAME SOCKET SOCKET ------------------------------------------------------------------------- 1 DCD DTR 4 20 3 RXD TD 3 2 4 RTS CTS 8 5 5 TXD RD 2 3 6 CTS RTS 7 4 7 DTR DCD (+DSR) 1 8 + 6 9 GND SG 5 7 PCB Pins 2,8,10 unused as before. I use 25 pin D's so that column is proven, but I applied the same logic to generate the 9 pin column. Why was the PC532 IDC configured as DTE ? possibilities include : - You can take ribbons straight from the PCB to modems. Remember multiple modem connection inspired the original PC532 design. - Maybe the PC/AT configuration was taken as `standard' for a host computer, but it's not, it has a screen that can run a terminal emulator, has just one or two ports normally, & is often connected via modem to a remote mainframe. Perhaps thats why IBM configured the PC/AT port as a DTE. - Laying out a PCB, it's easy to forget that the signal from the UART, via IDC,ribbon & D connector, that is called RD on the UART, actually needs to be connected to the pin known as TD on the D connector, to configure the D connector on the back of the box as DCE. You should also relabel all 4 RSTB (Pin 14) as RTSB on circuit sheets 6 & 7. I too would like to offer my compliments and thanks, both to George Scolaro for the hardware design, and all the other contributors who've paved the way up to (& hopefully beyond?) Minix. Abbrevs. used: DTE = Data Terminating Equipment (VDU/VDT/Terminal/Printer) DCE = Data Communicating Equipment (modems, & multiple port host computers) IDC = Insulation Displacement Connector Julian Stacey stacey@guug.de