On Sat, Aug 17, 2019 at 12:12 AM Charles via cctalk <cctalk@classiccmp.org> wrote: > Is there any standard pinout for 20 ma current loop using a DB-25 connector, > analogous to the well-documents RS-232 serial interface?
>From checking a couple of devices, I don't think so. Here's how the original IBM Async adapter for the 5150 did it... Pin 18 +receive current loop data Pin 25 -receive current loop return Pin 11 -transmit current loop data Pin 9 +transmit current loop return One BlackBox adapter I found used different pins. > The ADM-3A receives on pins 23 & 25, and transmits on pins 24 & 17. I'm used to using 15 and 17 for sync serial clock. They are typically NC for async. 23-25 have alternate uses that are, again, typically NC. (I've never seen a device that used pin 25 for 'test'). There are Sun workstations that have two serial ports over one DB25 which might be the only use of the "B" pins I've encountered. -ethan
