◆ Command parameters of INTBACK command

The command parameters for acquiring peripheral data using the INTBACK command are explained below.

● IREG0

There are two types of IREG0 settings: when the INTBACK command is issued and when a continue or break request is made.

(1) When issuing the INTBACK command

IREG0 is used for the SMPC status acquisition switch.

Figure 3.6 IREG0 (when the INTBACK command is issued)

IREG0	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
20100001H	SMPC status acquisition switch ( 00H or 01H ) Indefinite initial value / Write Only

IREG0: SMPC status acquisition switch setting value

IREG0 setting value	explanation
00H	Date and time, cartridge code, area code, terminal status, SMEM, Does not return each data of the reset button
01H	Date and time, cartridge code, area code, terminal status, SMEM, Returns each data of the reset button

When using the INTBACK command, be sure to set one of the above settings.

(2) When continue or break is requested

IREG0 is used for continue and break requests to SMPC.
The SMPC will start collecting the remaining peripheral data when there is a continue request. When there is a break request, the peripheral data collection is terminated and the INTBACK command is terminated.

Figure 3.7 IREG0 (when requesting continue and requesting break)

IREG0	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
20100001H	CONT	BR	−	−	−	−	−	−

CONT	: Continue request bit (continue request when inverted )
BR	: Break request bit (break request when set to "1B")
−	: Either "1B" or "0B" is acceptable

If a value that satisfies both the requirements of CONT and BR is written to IREG0, the operation of SMPC cannot guarantee which one to execute. (See Table 3.2)

● IREG1

IREG1 is used to set the peripheral data collection mode.

● IREG1

IREG1	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
20100003H	P2MD1	P2MD0	P1MD1	P1MD0	PEN	0	OPE	0
	Indefinite W	Indefinite W	Indefinite W	Indefinite W	Indefinite W	Indefinite ---	Indefinite W	Indefinite ---

Bits 7,6: Port 2 mode

Bit 7	Bit 6	explanation
P2MD1	P2MD0
0	0	15 byte mode
0	1	255 byte mode
1	0	SEGA RESERVED ( setting prohibited )
1	1	0 byte mode

Bits 5, 4: Port 1 mode

Bit 5	Bit 4	explanation
P1MD1	P1MD0
0	0	15 byte mode
0	1	255 byte mode
1	0	SEGA RESERVED ( setting prohibited )
1	1	0 byte mode

Bit 3: Peripheral data enable

Bit 3	explanation
PEN
0	Do not return peripheral data
1	Returns peripheral data

Bit 1: Optimization of peripheral data acquisition time

Bit 1	explanation
OPE
0	Optimize
1	Do not optimize

When using both SH-2 direct mode and SMPC control mode, use the port used in SH-2 direct mode when issuing the INTBACK command in 0-byte mode.

Example : Port 1 = SH-2 direct mode, port 2 = SMPC control mode, etc.

● IREG2

IREG2	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
20100005H	F0H Initial value: Indefinite Write Only

Be sure to set IREG2 to 0FH when issuing the INTBACK command.