Subject: Re: DIN to DB-9 cable From: Rubywand Date: Thu, Jul 30, 1998 23«52 EDT Message-id: <35C13F62.3EA0512@swbell.net> Julian Arevalo writes ... > > does anybody knows the pinout for a serial cable to connect an Apple IIc > (din connector) to a PC (DB-25 connector)? > Below is some cable info from the newsgroup FAQs at ... ftp://ground.ecn.uiowa.edu/2/apple2/Faqs/ >> [file- Csa2T1tcom.txt] From: David Empson 017- What kind of cable should I use to connect a modem to my IIc? Here is the pinout of the IIc serial port. Looking at the computer from the back, the pins are numbered: 5 1 4 2 3 The functions are: 1 Handshake Out (nominally DTR) 2 Data Out (TxD) 3 Ground 4 Data In (RxD) 5 Handshake In (nominally DSR) To wire up a IIc to a simple modem without hardware handshaking, use the following pinout: IIc Modem DIN-5 DB-25M 1 ----- 20 DTR 2 ----- 2 TxD 3 ----- 7 Gnd 4 ----- 3 RxD 5 ----- 6 DSR (you might want to use pin 8, DCD in some cases) The IIc cannot do hardware handshaking very well, but this is as close as you can get: IIc Modem DIN-5 DB-25M 1 ----- 4 RTS 2 ----- 2 TxD 3 ----- 7 Gnd 4 ----- 3 RxD 5 ----- 5 CTS The IIc's handshaking lines have annoying side effects, which cause problems with hardware handshaking: 1. The "Handshake Out" signal is implemented to mean "I want to send data" (the official and original meaning of RTS). If you turn off the output handshake line, the IIc will stop sending data. For a hardware handshaking modem, RTS is supposed to mean "You are allowed to send me data" (from the computer's point of view). If the computer tells the modem to stop transmitting, the computer will also be unable to transmit. This will reduce the rate at which data can be transferred bidirectionally, but doesn't cause any other problems. 2. The "Handshake In" signal is implemented to mean "There is receive data present" (the official meaning of DCD). If the incoming handshake line is disabled, the IIc will stop receiving data (ignore any data on RxD). For a hardware handshaking modem, CTS is supposed to mean "You are allowed to send me data" (from the modem's point of view). If the modem tells the computer to stop transmitting, the computer will also be unable to receive, and will discard any data sent by the modem while CTS is not active. This can cause screen corruption and loss of data blocks or acknowledgements during a file transfer, which will require retransmission. It is only likely to be a problem while a lot of data is being sent, so is more likely to cause problems during a file upload than a download. If the comms software is quick enough, it can drop RTS immediately when CTS is lowered, which will prevent the modem from sending any more data. The original IIc motherboard has another problem: it uses a cheap method of generating the clock frequency for the serial ports. Most implementations based on the 6551 chip use a 1.8432 MHz crystal, which gives exact baud rates, but the IIc takes the master system clock (14.31818 MHz in an American IIc) and divides it by eight to produce 1.7898 MHz. The 3% decrease in clock frequency produces a 3% drop in the baud rate, which is enough to prevent operation with some serial devices, particularly intelligent modems running at 1200 bps or faster. This not always a problem, and I have successfully used one of these IIc's with a ZyXEL U-1496E modem and a direct connection to a IIgs at 9600 bps. I have had problems in other cases. You cannot identify whether you have this motherboard except by opening up the computer and looking for a tell-tale component. (I don't have the details handy.) You can make a reasonable guess at whether you have the original motherboard by checking which firmware version is installed in the IIc. Get into BASIC, and type PRINT PEEK(64447). If the value displayed is 255, then you have the original ROM, and almost certainly have the original motherboard, though it might have been modified to use a crystal. If the value displayed is 0, then you might have the original motherboard or the revised one. (This ROM version supports the UniDisk 3.5 drive.) If the value displayed is 3 or 4, then you have the "memory expansion" version of the firmware, and almost certainly have the latest motherboard, which includes a memory expansion slot under the keyboard. In theory, the IIc's maximum baud rate is 19200. Whether it can actually keep up with that rate is another question. 9600 should be fine. << > also what software should I use to transfer 51/4 disks to *.dsk images, adn > where can I download It form? > You can download DSK2FILE at http://keaggy.intmed.mcw.edu/dsk2file.html . Rubywand