mark@sickkids.UUCP (Mark Bartelt) (05/03/88)
One of the researchers down the hall recently acquired a Masscomp 55S. (Or is it a 5500S? The purchase order and the tag on the back of the CPU box use the former designation, whereas the maintenance agreement uses the former.) Whichever, there is a weirdness with the serial ports, which Masscomp hasn't yet given us an answer to: Needing dialin access, we hooked up a standard modem to the "REMOTE" port, and succeeded in dialing in once. Following that, things would no longer work: The modem would answer, but immediately drop carrier. After a bit of poking around, we found that the Masscomp's REMOTE port had something odd on its DTR line: A perfect square wave, amplitude 10V, period approximately 9.174 KHz. No wonder the modem was confused! There was also a nice square wave, amplitude 8V, period approximately 292.4 Hz, on the "LOCAL" port. The "PRINTER" port looked fine. The field service person arrived, and swapped the CPU board. (As to *why* Masscomp would design a system that requires that the CPU board be swapped when a serial port goes out to lunch is another question.) This fixed the problem. But, unfortunately, the problem reappeared as soon as we dialed in again! The modem<=>computer cable connects the standard RS232 pins: 2,3,4,5,6,7,8,20,22. I suspect that there may something nonstandard about Masscomp's serial ports, and that perhaps transition from -10V to +10V (or vice versa) on pin 22 ("RING") breaks something. Of course, there is nothing in any of the documentation that we received that tells you which pins they *want* connected when you hook a modem up to the "REMOTE" port. Masscomp, of course, seems reluctant to keep swapping CPU boards, only to have them break again. But on the other hand, we know it's not the modem's fault. We could proceed by trial and error (e.g. as a first attempt, try not connecting pin 22), but I suspect that someone must have already encountered this problem. Does anyone have a quick and ready answer? Thanks in advance. --- Mark Bartelt UUCP: {utzoo,decvax,ihnp4}!sickkids!mark Hospital for Sick Children, Toronto BITNET: mark@sickkids.utoronto 416/598-6442 INTERNET: mark@sickkids.toronto.edu [ Note: The internet address is claimed to work, but has not yet been tried. ]
mark@sickkids.UUCP (Mark Bartelt) (05/03/88)
One of the researchers down the hall recently acquired a Masscomp 55S. (Or is it a 5500S? The purchase order and the tag on the back of the CPU box use the former designation, whereas the maintenance agreement uses the former.) [ The price list calls it the 55S. The marketing folks call it the 5520 S. Your guess is as good as mine. - sob] Whichever, there is a weirdness with the serial ports, which Masscomp hasn't yet given us an answer to: Needing dialin access, we hooked up a standard modem to the "REMOTE" port, and succeeded in dialing in once. Following that, things would no longer work: The modem would answer, but immediately drop carrier. After a bit of poking around, we found that the Masscomp's REMOTE port had something odd on its DTR line: A perfect square wave, amplitude 10V, period approximately 9.174 KHz. No wonder the modem was confused! There was also a nice square wave, amplitude 8V, period approximately 292.4 Hz, on the "LOCAL" port. The "PRINTER" port looked fine. The field service person arrived, and swapped the CPU board. (As to *why* Masscomp would design a system that requires that the CPU board be swapped when a serial port goes out to lunch is another question.) [The serial ports are on the CPU board. This is the case with many other manufacturers of small UNIX computers! - sob] This fixed the problem. But, unfortunately, the problem reappeared as soon as we dialed in again! The modem<=>computer cable connects the standard RS232 pins: 2,3,4,5,6,7,8,20,22. I suspect that there may something nonstandard about Masscomp's serial ports, and that perhaps transition from -10V to +10V (or vice versa) on pin 22 ("RING") breaks something. Of course, there is nothing in any of the documentation that we received that tells you which pins they *want* connected when you hook a modem up to the "REMOTE" port. Masscomp, of course, seems reluctant to keep swapping CPU boards, only to have them break again. But on the other hand, we know it's not the modem's fault. We could proceed by trial and error (e.g. as a first attempt, try not connecting pin 22), but I suspect that someone must have already encountered this problem. Does anyone have a quick and ready answer? Thanks in advance. --- Mark Bartelt UUCP: {utzoo,decvax,ihnp4}!sickkids!mark Hospital for Sick Children, Toronto BITNET: mark@sickkids.utoronto 416/598-6442 INTERNET: mark@sickkids.toronto.edu [The UUCP Management Guide (ORDER NUMBER: M-UUCP-MG), which is shipped with most new systems, has information on how to hook up a modem in Section 3.3. It advises that 1,2,3,4,5,6,7,8, and 20 should be hooked up. -- sob]