phil@scubed.UUCP (07/04/86)
I recently posted a note detailing my experience with flow control on the Amiga serial port. I had to hotwire pin 5 on my plotter to pin 18 on the Amiga in order for the CTS handshaking to work. Last night I was working on the Amiga and not using the plotter so I did not power it on. Guess what! The machine would not kickstart until I unplugged the cable going to the plotter. Turn the plotter on or unplug the cable and everything works fine. After the machine is up and running, you still need to power on the plotter or unplug the cable or whatever you are running will lockup. This is true even if the application does not use the serial port. Again, if I power on the plotter or unplug the cable all returns to normal. Do any of you understand what is going on here? Phil
kim@mips.UUCP (07/07/86)
> I recently posted a note detailing my experience with flow control > on the Amiga serial port. I had to hotwire pin 5 on my plotter to > pin 18 on the Amiga in order for the CTS handshaking to work. > > Last night I was working on the Amiga and not using the plotter > so I did not power it on. Guess what! The machine would not > kickstart until I unplugged the cable going to the plotter. > Do any of you understand what is going on here? Hmmmm ... pin 18 of the serial port (Amiga side) is listed as being signal INT2* in Appendix-E of the Hardware Manual. Since the signal is an "active low" signal (the "*" in its name), I would guess that with the plotter off (but connected), this line is being pulled down, and is causing Interrupt2 to the processor to be asserted continuously. With the plotter disconnected, the signal is most likely being pulled-up (or at least floats high), and thus no rupt occurs. I've no idea why your plotter needs its CTS hooked-up to INT2* to work though. /kim -- UUCP: {decvax,ucbvax,ihnp4}!decwrl!mips!kim DDD: 408-720-1700 x231 USPS: MIPS Computer Systems Inc, 930 E. Arques Av, Sunnyvale, CA 94086 CIS: 76535,25
carolyn@cbmvax.cbm.UUCP (Carolyn Scheppner) (07/07/86)
In article <85@scubed.UUCP> phil@scubed.UUCP (Phil Cohen) writes: >I recently posted a note detailing my experience with flow control >on the Amiga serial port. I had to hotwire pin 5 on my plotter to >pin 18 on the Amiga in order for the CTS handshaking to work. > >Last night I was working on the Amiga and not using the plotter >so I did not power it on. Guess what! The machine would not >kickstart until I unplugged the cable going to the plotter. >Turn the plotter on or unplug the cable and everything works fine. > >After the machine is up and running, you still need to power on the >plotter or unplug the cable or whatever you are running will lockup. >This is true even if the application does not use the serial port. >Again, if I power on the plotter or unplug the cable all returns to >normal. > >Do any of you understand what is going on here? > >Phil I'm not a hardware type but here's my guess. Pin 18 of the Amiga's RS-232 port is documented as INT2* (normally high interrupt line). Your plotter's pin 5 must be normally high, going low when it's buffers are full, stopping not just serial transmission but whatever else runs off INT2. When your plotter is off, it is not holding pin 5 high and grounds INT2*, freezing PORTS (8520A, external2) interrupts. I don't think this a good place to connect your pin 5. What are the ready and not-ready voltages put out by your pin 5 ? There should be a way to hook it to the Amiga hardware handshaking lines (CTS/RTS). You will have to disable software (XON/XOFF) handshaking and enable hardware handshaking using a program like setserial or Beta 1.2 Preferences. -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Carolyn Scheppner -- CBM >>Amiga Technical Support<< UUCP ...{allegra,caip,ihnp4,seismo}!cbmvax!carolyn PHONE 215-431-9180 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=