axaris@acsu.buffalo.edu (vassilios e axaris) (08/10/90)
Hello, I would like to know the connections from the UART pins to the port connectors, as used for COM1/2 in pcs. Thanks in advance, Vassilio E. Axaris
dgil@pa.reuter.COM (Dave Gillett) (08/10/90)
In <32464@eerie.acsu.Buffalo.EDU> axaris@acsu.buffalo.edu (vassilios e axaris) writes: >I would like to know the connections from the UART pins to the port connectors, >as used for COM1/2 in pcs. Well, as I understand it the UART doesn't connect directly to the DB-9/DB-25 pins, but goes through a 1488/1489 pair which handle details like conversion between TTL and RS-232C voltage levels. That said, here are the 8250 pinouts that correspond to RS-232C signals, as per page 501 of _The Programmer's PC Sourcebook_, by Thom Hogan: 8250 pin Name DB-25 pin 11 TxD 2 10 RxD 3 32 RTS 4 36 CTS 5 37 DSR 6 20 Signal Ground 7 ~29 CD 8 33 DTR 20 39 RI 22 I'm not positive about pin 29; Hogan calls it "No Connection", but we know there's a bit in one of the 8250 registers that corresponds to Carrier Detect and I don't see any other possibilities. DB-25 pin 23, Data Rate Selector, may be in some sense analogous to 8250 pin 15, ~Baud Out. And 8250 pin 9, RCLK, may possibly correspond to one of the optional clock lines in RS-232, but I can't tell which one. I've never seen any of these used. Dave
darcy@druid.uucp (D'Arcy J.M. Cain) (08/12/90)
In article <315@saxony.pa.reuter.COM> dgil@pa.reuter.COM (Dave Gillett) writes: >In <32464@eerie.acsu.Buffalo.EDU> axaris@acsu.buffalo.edu (vassilios e axaris) writes: >>I would like to know the connections from the UART pins to the port connectors, >>as used for COM1/2 in pcs. First of all if you are doing this sort of thing you should have a copy of the spec sheet and not rely and second hand information however ... > >Well, as I understand it the UART doesn't connect directly to the DB-9/DB-25 >pins, but goes through a 1488/1489 pair which handle details like conversion >between TTL and RS-232C voltage levels. > True >That said, here are the 8250 pinouts that correspond to RS-232C signals, as per >page 501 of _The Programmer's PC Sourcebook_, by Thom Hogan: > 8250 pin Name DB-25 pin > 11 TxD 2 > 10 RxD 3 > 32 RTS 4 > 36 CTS 5 > 37 DSR 6 > 20 Signal Ground 7 > ~29 CD 8 > 33 DTR 20 > 39 RI 22 > >I'm not positive about pin 29; Hogan calls it "No Connection", but we know >there's a bit in one of the 8250 registers that corresponds to Carrier Detect >and I don't see any other possibilities. > Pin 29 on the 8250 is NC. The DCD pin is 38. >DB-25 pin 23, Data Rate Selector, may be in some sense analogous to 8250 pin >15, ~Baud Out. And 8250 pin 9, RCLK, may possibly correspond to one of the >optional clock lines in RS-232, but I can't tell which one. I've never seen > any of these used. NO. -- D'Arcy J.M. Cain (darcy@druid) | D'Arcy Cain Consulting | MS-DOS: The Andrew Dice Clay West Hill, Ontario, Canada | of operating systems. + 416 281 6094 |