PROPOSED: adding a TIMEOUT to PRINT_SERIAL.ASM

[dbrucemoore]

Currently, the BASIC ROM code expects a handshake from a connected serial device. If that device is connected but not powered on (or defective) the OS gets stuck in loop waiting for the device to respond.

It appears PRINT_SERIAL uses the same code base:

                LA2F3          LDB         PIA1+2          ; WAIT FOR HANDSHAKE
                               LSRB                              ; CHECK FOR R5232 STATUS?
                               BCS         LA2F3             ; NOT YET READY

I propose a time-out that returns an error code, readable by BASIC, to a location like DSKCON ($F0).

besides the code not "hanging", the error code could be used to notify the User to "power-up" the serial device, or that it has a hardware issue.

[dbrucemoore]

something like this code would work

START	EQU	*

	PSHS	B,A,CC
	ORCC	#$50	;disable irq,firq
	CLR	KEYIN	;store status here,default 0= CoCoMp3 not found
	LDA	#255	;counter for CoCoMp3 check
Loop	DECA
	BEQ	LoopExit
	LDB	$FF22	;PIA1	
	LSRB		;move serial bit to CC
	BCS	Loop
	INC	KEYIN	;1=CoCoMp3 found
	
LoopExit	ANDCC	#$AF	;enable irq,firq
	PULS	CC,A,B```