A few PCjs machines, such as the one below, have enabled TestMonitor support, allowing you to use one of the machine’s serial ports (usually COM2) to control and issue commands to the machine.
After the machine finishes booting to a DOS prompt, type the DOS command
CTTY COM2, and then you can interact with
the machine via the TestMonitor window.
Ctrl-T in that window toggles it between “terminal mode” and “prompt mode”. After the initial
the TestMonitor should detect the DOS prompt and enter “dos mode”, at which point you can type the command
enter “debug mode”, where a number of debug macros are available to you, such as:
cursor 11 13(programs the default EGA cursor)
cursor 4 19(programs a block cursor)
cursor 4 20(programs a single-line cursor; see this PCjs blog post)
To see all the command modes, and the macros available in each mode, see tests.json.
There is also a TestMonitor Utility that can be used to control a physical PC from the command-line. When using a physical PC, the INT14.ASM Terminate-and-Stay-Resident (TSR) utility should be installed, to minimize the risk of dropped characters when using the DOS “CTTY” command.
[PCjs Machine "ibm5170"]
Waiting for machine "ibm5170" to load....
Volume in drive A is INT14 Directory of A:\ DOWNLOAD ASM 10032 3-22-20 10:57p DOWNLOAD COM 1826 3-08-20 12:38a FAKECTTY ASM 2796 3-08-20 12:38a FAKECTTY COM 307 3-08-20 12:38a INT14 ASM 12480 3-08-20 12:38a INT14 COM 2335 3-08-20 12:38a MK BAT 219 3-08-20 12:38a 7 file(s) 29995 bytes 128512 bytes free