Hi All, after some distraction on other projects I picked up my pdp8/e simulator that runs on the 6809 Core Board. When I stopped a few months ago, I got the simulator working (as far as I can know with my very limited pdp8/e knowledge), but the console (yes, blinkenlights!) crashed the software. That problem is fixed, but what I can not get clear from the books is the active position of the HALT and SING-STEP switches. When the Switch Register switches are "down" they produce a logic zero; the "up" position present logic ones. Likewise for the SW switch. The momentary switches CLEAR, CONT, and EXAM are "up" in their normal position, but in that 'block' are also two switches: HALT and SING-STEP. Are these two active in the "up" or the "down" position? TIA, - Henk, PA8PDP.