Using the PacComm PC-100 boards with NOS These procedures were established using a PC-105D board, which is apparently the same as a PC-100, but without the 7910. Thus they're useful for 1200 baud only. If you have a PC-100 (with 7910), the values below should work if you want to use it (port A of the 8530), but I haven't tried it. The board I was testing had the DCD state machine mod: I assume results will be similar for boards not so equipped, but, again, I have no way of testing it. The version of NOS for which these remarks apply is v1.7h. I assume that something similar will apply to other versions. 1. Hardware setup: A. Jumpers Firstly, the jumpers must be set up correctly. The two large jumper blocks which set up the 8530 clocks (JP-1 and JP-2) should have jumpers 1, 3, 7 and 9 installed (counting from the left, with the edge connector at the bottom) for operation with the internal modems. JP-3 sets the hardware interrupt vector used. Select one which isn't used by any other card, remembering the following: - IRQ2 is used by EGA, VGA and (presumably) higher video boards; - IRQ3 and IRQ4 are used by COM2 and COM1 respectively; - IRQ5 is used by the hard drive controller in an XT, but is free on an AT-class machine; - IRQ6 is used by the floppy disk controller; - IRQ7, dedicated to LPT1:, is usually nevertheless available. JP-4 sets the base address of the card. See the manual for details. Pick an address which, once again, isn't used by anything else. JP-5 isn't used unless you're connecting external clocks to the 8530. In this case you're on your own. You'll need a PC-100 manual, an 8530 manual, and lots of patience. JP-6 and JP-7 select the operating mode of the TCM3105 modem chip. The manual claims that they should not be both installed at the same time. The board I had came with a wire link soldered into JP-6, and JP-7 was used for some connections to the DCD board. I left it that way. JP-8 selects the clock source. Install it on the "ONBD" side, which uses the on-board 4.9 MHz crystal. B. Trimpot Adjustment. Both the 3105 and the 7910 modems contain adjustments for transmit and receive level, and the 3105 has additional adjustments for carrier detect level and bias distortion. Unless you know you're having problems, it's best not to touch these (assume they're set properly at the factory). If, on the other hand, you feel that adjustment is necessary, the following may help: (i) Transmit level (R9 for 7910 (channel A), R11 for TCM3105 (ch. B)). The whole subject of the correct modulation to use on an FM channel is too complicated to go into here. Let's assume that you've set the transmitter for correct modulation level: then we only need to ensure that we don't overload the audio input circuits of the transmitter. One way do this is to monitor the transmitter's output with a receiver and, starting with the level pot at minimum, wind it up until no further increase in audio level (in the receiver) is heard. Leave the pot set at this position. (ii) Receive level (R8 for 7910, R10 for TCM3105). Adjustment of this is not critical -- the 7910, for example, will run on the smell of an oily rag. Set it about half-way and it should be close. If the carrier detect signal never becomes true, then increase this adjustment. (iii) Bias Distortion (TCM3105 only -- R12). An oscilloscope is required to set this adjustment. One way of doing it is to supply continuous ping packets with lots of data to the receiver ("ping 200 5000" works fine). An easy way to do this is to loop back the transmitter to the receiver and enter the ping command into NOS. Monitor the RXD pin of the 3105 (pin 8) and watch the packets. Most of the packet will consist of the dummy data -- which is essentially a 1:1 mark/space ratio signal. Adjust the pot until this data appears as square wave (i.e. the positive and negative transitions are of equal length). (iv) Carrier detect level (TCM3105 only -- R13). This is best adjusted using an audio generator. Inject 1300 Hz (the mark frequency for CCITT V23) into the audio input of the board, and monitor pin 3 (CD) of the 3105. If the level on this pin isn't high (say 3-4 volts or so), adjust R13 until it is. (You may need to increase the level out of the generator to achieve this). Now switch off the generator and adjust R13 until the voltage on the pin goes low. This setting should be adequate. 2. Software setup: This consists of adding the appropriate attach commands to autoexec.nos. First initialise the board: attach scc 1 init
0 6 4 1 0 p4915200 2 where
is the base address of the board. Note that the manual states that all addresses end with 4: this actually refers to the address of the 8530. We need to specify the address of the latch here, which is xx0. For example, with only the left-hand jumper installed on JP-4, the manual claims the address is 2e4 (hex). The value for the attach command, however, is 2e0. (Note that the prefix "0x" is optional). is the interrupt vector as set on the board (JP-3). See comments above for how to select this. is the value to be set in the latch. This is used to select the operating mode of the modem. The following values set the TCM3105 (channel B) to 1200/1200 baud, and the 7910 to the values stated: 0x88 for 300 baud (assuming Bell 103 answer mode), 0x82 for 1200 baud (Bell 202, or 0x8a with the equalizer) 0x86 for 1200 baud (CCITT v23, or 0x8e with the equalizer) Note that this approach doesn't use the INTACK signal. In a system with a single 8530 there's not much point to it, and in any case I found it didn't work with the standard SCC driver. I was able to get it to work by modifying the sources, but for now it's probably safest not to use it. If you must try it, however, use the following attach command instead: attach scc 1 init
0 6 4 1 p4915200 2 where =
+ 8 (e.g. if
== 2e0, = 2e8). Then perform the actual attach. There are, of course, lots of possibilities. This command sets channel A up as a 4800 baud SLIP link to another computer (note that this doesn't use the 7910 chip: connect using the RS-232 pins): attach scc 0 slip pc0 576 4800 8192 This command sets channel B (the 3105) to perform a 1200 baud AX25 link (probably the most common use of this board): attach scc 1 ax25 pc1 256 d1200 1024 The following possibilities, using channel A (the 7910), haven't been tried, but should work. Ensure that the correct latch value has been set in the attach ... init command. Set up channel A to perform a 300 baud AX25 link: attach scc 0 ax25 pc0 256 d300 1024 Set up channel A to perform a 1200 baud ax25 link: attach scc 0 ax25 pc0 256 d1200 1024 - Ron Murray 1/12/91 Please send comments, queries, complaints, money etc. to: Packet radio: VK6ZJM@VK6XPS.#WA.AUS.OC Internet: nmurrayr@cc.curtin.edu.au