Hi! Does anyone know what hardware Motorola originally used to demonstrate the 6809? I am referring to the hardware Motorola references in the 6809 programming manual. It is the hardware that Motorola wrote their ASSIST09 debug monitor to run on. The reason I am asking is to understand how they are connecting the output of timer #1 of the MC6840 PTM to the CPU /NMI line. Specifically, is it directly connected or inverted? Is other logic involved or further qualifications? Does anyone have schematics available of the original Motorola 6809 hardware? The ASSIST09 source code implies a direct connection but that is counter intuitive to me since the /NMI line is active low and the PTM timer #1 is active high. The ASSIST09 monitor uses the PTM connected to the /NMI line for hardware assisted tracing. According to the datasheet for the 6809 and 6840, the /NMI is activated on the negative transition which would be on the falling edge of the pulse from the PTM timer output if directly connected. If inverted, it would be on the leading edge of the pulse. The reason I need this information is I am building an IO mezzanine board (ACIA, PTM, dual VIAs) for the N8VEM 6809 host processor. The good news is that I've seen the hardware assisted tracing work using the inverted output of the timer. However, the IO mezzanine is connected to the 6809 host processor by ribbon cables which are notorious for causing signal delays and other problems. As a result, the tracing is unreliable and I would like to fault isolate. The rest of ASSIST09 seems to be working reliably on my prototype hardware. Originally, I presumed Motorola designed the ASSIST09 monitor for the EXORset system since it was their first 6809 based computer and released about the same time as the 6809's introduction. If anyone has familiarity with the original Motorola hardware for the ASSIST09 debug monitor I would appreciate your help. Thanks in advance and have a nice day! Andrew Lynch I refer to these two functions in the ASSIST09 source code: ************************************************** * [SWI FUNCTION 8] * MONITOR ENTRY * FIREUP THE ASSIST09 MONITOR. * THE STACK WITH ITS VALUES FOR THE DIRECT PAGE * REGISTER AND CONDITION CODE FLAGS ARE USED AS IS. * 1) INITIALIZE CONSOLE I/O * 2) OPTIONALLY PRINT SIGNON * 3) INITIALIZE PTM FOR SINGLE STEPPING * 4) ENTER COMMAND PROCESSOR * INPUT: A=0 INIT CONSOLE AND PRINT STARTUP MESSAGE * A#0 OMIT CONSOLE INIT AND STARTUP MESSAGE ************************************************* SPC 1 SIGNON FCC /ASSIST09/ SIGNON EYE-CATCHER FCB EOT SPC 1 ZMONTR STS <RSTACK SAVE FOR BAD STACK RECOVERY TST 1,S ? INIT CONSOLE AND SEND MSG BNE ZMONT2 BRANCH IF NOT JSR [VECTAB+.CION,PCR] READY CONSOLE INPUT JSR [VECTAB+.COON,PCR] READY CONSOLE OUTPUT LEAX SIGNON,PCR READY SIGNON EYE-CATCHER SWI PERFORM FCB PDATA PRINT STRING ZMONT2 LDX <VECTAB+.PTM LOAD PTM ADDRESS BEQ CMD BRANCH IF NOT TO USE A PTM CLR PTMTM1-PTM,X SET LATCH TO CLEAR RESET CLR PTMTM1+1-PTM,X AND SET GATE HIGH LDD #$01A6 SETUP TIMER 1 MODE STA PTMC2-PTM,X SETUP FOR CONTROL REGISTER1 STB PTMC13-PTM,X SET OUTPUT ENABLED/ * SINGLE SHOT/ DUAL 8 BIT/INTERNAL MODE/OPERATE CLR PTMC2-PTM,X SET CR2 BACK TO RESET FORM * FALL INTO COMMAND PROCESSOR SPC 3 *******************TRACE - TRACE INSTRUCTIONS ******************* . - SINGLE STEP TRACE CTRACE BSR CDNUM OBTAIN TRACE COUNT STD <TRACEC STORE COUNT CDOT LEAS 2,S RID COMMAND RETURN FROM STACK CTRCE3 LDU [10,S] LOAD OPCODE TO EXECUTE STU <LASTOP STORE FOR TRACE INTERRUPT LDU <VECTAB+.PTM LOAD PTM ADDRESS LDD #$0701 7,1 CYCLES DOWN+CYCLES UP STD PTMTM1-PTM,U START NMI TIMEOUT RTI RETURN FOR ONE INSTRUCTION SPC 3