PCjs Machines

Home of the original IBM PC emulator for browsers.

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Ohio Scientific Challenger 1P with Debugger

C1Pjs is a JavaScript simulation of the Ohio Scientific Challenger 1P, an 8-bit 6502-based microcomputer manufactured in 1978. The base configuration included an 8Kb BASIC-in-ROM from Microsoft and 4Kb of RAM (user-expandable to 8Kb). Below is a simulation of the 8Kb RAM configuration.

OSI Challenger 1P with Debugger

Challenger 1P
PCjs Debugger
A
0000
X
0000
Y
0000
S
0000
PC
0000
C
0
Z
0
I
0
D
0
B
0
V
0
N
0
Speed:
Stopped
C1Pjs v2.21 © 2012-2023 Jeff Parsons

Using The Debugger

Type ? and then Enter to display the list of Debugger commands.

Press the Step button while the simulated CPU is halted to execute a single instruction; hold the Step button to step through multiple instructions.

The instruction frequency (“f”) and history (“p”) commands collect data only while the CPU is running (not stepping) and one or more breakpoints have been set; set a dummy execution breakpoint (eg, “bp 0”) to enable collection.

[GitHub Source]