K12MIT on PDP-12

On Thu, 25 Nov 2021, Christian Corti wrote: I've found the bug. Charles Lasner broke PDP-12 support (and probably also older PDP-8 models like 8/I) with his additions to support the DECmate family. The location is at 0206, labelled SETBAUD. This should be a NOP on standard systems, but is overlayed by an IOT to set the baud rate on a DECmate 1. This results in a 6413 instruction (because I have assembled it for the second serial port on 40/41). This instruction always skips (as the transmitter done flag is always set), thus jumping into a 4411 that is the address of a CRLF to be printed but executed as a JMS into nirvana. The very same code runs fine on a PDP-8/E with a KL8/E interface that apparently either ignores this instruction or, by other means, has the flag cleared. If patching location 0206 to 7000 (NOP), K12MIT will run on a PDP-12. Sending files works, but receiving seems to be broken. Most of the times, the sending Kermit aborts the transfer to the PDP-12 with a out-of-window-NACK error (confirmed by looking at the protocol debug log). K12MIT sends a NACK to a previous packet that it already ACK'ed *after* receiving the next data packet. Here's the code fragment: 1827 000200 5777 CLOOP, JMP I (INITIALIZE) /**** INITIALIZED **** CLA CLL /024 CJL 1828 000201 4577 JMS I [CRESET] /RESET CONSOLE ROUTINE STUFF 1829 000202 3002 DCA ABFLAG /CLEAR ABORT FLAG /044 CJL 1830 000203 3105 DCA REMWAIT /CLEAR REMOTE FLOW CONTROL WAIT /049 CJL 1831 000204 4324 CLDMZAP,JMS DMINIT /INITIALIZE DECMATE PORT /048 CJL 1832 1833 / THE PREVIOUS INSTRUCTION IS FOR DECMATE OPERATION ONLY. THE DEFAULT 1834 / INSTRUCTION IS FOR KL8 INTERFACES ONLY. 1835 1836 0204 *CLDMZAP /OVERLAY DECMATE CODE /048 CJL 1837 1838 000204 7000 CLDMZAP,NOP /DON'T INITIALIZE DECMATE PORT /048 CJL 1839 000205 1007 TAD RATE /GET BAUD RATE 1840 000206 6363 SETBAUD,MSB /SET REMOTE BAUD RATE /050 CJL 1841 1842 / THE PREVIOUS INSTRUCTION IS FOR DECMATE II OPERATION ONLY. /050 CJL 1843 1844 0206 *SETBAUD /OVERLAY DECMATE II CODE /050 CJL 1845 1846 000206 7000 SETBAUD,NOP /NOT APPLICABLE ON DECMATE I /050 CJL 1847 1848 / THE PREVIOUS INSTRUCTION IS FOR DECMATE I OPERATION ONLY. THE DEFAULT 1849 / INSTRUCTION IS FOR KL8 INTERFACES ONLY. 1850 1851 0206 *SETBAUD /OVERLAY DECMATE I CODE /050 CJL 1852 1853 000206 6413 SETBAUD,RSBIOT /SET REMOTE BAUD RATE /050 CJL 1854 000207 4576 JMS I [SCRIBE] /DO A /025 CJL 1855 000210 4411 CRLF /<CR>, <LF> /025 CJL 1856 000211 4576 JMS I [SCRIBE] /GIVE THEM THE /025 CJL 1857 000212 4457 PRMTMSG /PROMPT MESSAGE /025 CJL 1858 000213 4776 JMS I (LININP) /GET INPUT LINE FROM USER Christian