Motorola MVME166D2, MVME166IG/D2 manual Using 166Bug Target Vector Table

Using the 166Bug Debugger

Example: Trace one instruction using debugger.

	166Bug>RD
	PC	=00010000	SR		=2700=TR:OFF_S._7_				VBR	=00000000
	USP	=0000DFFC	MSP		=0000EFFC ISP* =0000FFFC				SFC	=0=F0
	DFC	=0=F0	CACR		=0=
	D0	=00000000	D1		=00000000		D2	=00000000	D3	=00000000
	D4	=00000000	D5		=00000000		D6	=00000000	D7	=00000000
4
	A0	=00000000	A1		=00000000		A2	=00000000	A3	=00000000
	A4	=00000000	A5		=00000000		A6	=00000000	A7	=0000FFFC
	00010000 203C0000			0001		MOVE.L		#$1,D0
	166Bug>T
	PC	=00010006	SR		=2700=TR:OFF_S._7_				VBR	=00000000
	USP	=0000DFFC	MSP		=0000EFFC ISP* =0000FFFC				SFC	=0=F0
	DFC	=0=F0	CACR		=0=
	D0	=00000001	D1		=00000000		D2	=00000000	D3	=00000000
	D4	=00000000	D5		=00000000		D6	=00000000	D7	=00000000
	A0	=00000000	A1		=00000000		A2	=00000000	A3	=00000000
	A4	=00000000	A5		=00000000		A6	=00000000	A7	=0000FFFC
	00010006 D280					ADD.L		D0,D1
	166Bug>

Notice that the value of the target stack pointer register (A7) has not changed even though a trace exception has taken place. Your program may either use the exception vector table provided by 166Bug or it may create a separate exception vector table of its own. The two following sections detail these two methods.

Using 166Bug Target Vector Table

The 166Bug initializes and maintains a vector table area for target programs. A target program is any program started by the bug, either manually with GO or TR type commands or automatically with the BO command. The start address of this target vector table area is the base address of the debugger memory. This address is loaded into the target-state VBR at power up and cold-start reset and can be observed by using the RD command to display the target-state registers immediately after power up.

4-12 MVME166 Single Board Computer Installation Guide