Update dbgmon.asm

Source/Apps/ramtest/dbgmon.asm

@@ -908,6 +908,31 @@ FILL_MEM:
 
 DORAMTEST:
 
+; VERIFY DATA BUS FUNCTIONALITY BEFORE STARTING MEMORY TEST
+	LD	A,$80			; FIRST 32KB PAGE ONLY
+	LD	(PAGE_NUM),A		; STORE WORKING PAGE NUMBER
+	OUT	(MPCL_ROM),A		; SWITCH OUT LOWER 32KB ROM PAGE
+	OUT	(MPCL_RAM),A		; SWITCH IN LOWER 32KB RAM PAGE
+	LD	A,$00			; INITIALIZE A TO 0
+
+DATABUSCHECK:
+	LD	($0000),A		; WRITE TO LOWEST RAM ADDRESS
+	LD	C,($0000)		; READ VALUE FROM LOWEST RAM ADDRESS
+	CP	C			; IS IT SAME AS WRITTEN?
+	JP	NZ,DATABUSFAIL		; DATA BUS FAIL HANDLER ROUTINE
+	INC	A			; GET NEXT VALUE
+	JP	NZ,DATABUSCHECK		; REPEAT FOR ALL 256 VALUES
+	
+DATABUSFAIL:
+	PUSH	A			; STORE FAILED VALUE
+	LD	HL,TXT_DATA_BUS_FAIL	; POINT AT DATA BUS FAIL TEXT
+	CALL	MSG			; PRINT DATA BUS FAIL LABEL
+	POP	A			; RETRIEVE FAILED VALUE
+	CALL	HXOUT			; SHOW VALUE THAT FAILED
+	LD	HL,TCRLF		; CR & LF
+	CALL	MSG			; DISPLAY IT
+	JP	SERIALCMDLOOP		; AND BACK TO COMMAND LOOP
+
 MEMSIZELOOP:
 	LD	HL,TXT_RAM_TEST_MAIN	; POINT AT RAM TEST MAIN MENU TEXT
 	CALL	MSG			; PRINT MENU TEXT LABEL
@@ -1139,6 +1164,11 @@ TXT_RAM_FAIL:
 	.DB   "RAM FAIL, 32KB PAGE NUMBER: "
 	.DB   CR,LF,ENDT
 
+TXT_DATA_BUS_FAIL:
+	.DB   CR,LF
+	.DB   "DATA BUS FAIL, VALUE ="
+	.DB   ENDT
+
 TXT_SKIP_16:
 	.DB   CR,LF
 	.DB   "SKIPPING PAGE 0F "