◆Command parameters of INTBACK command

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

●IREG0

There are two types of IREG0 settings: when issuing an INTBACK command and when requesting a continue or break.

(1) When issuing the INTBACK command

IREG0 is used for the SMPC status acquisition switch.

Figure 3.6 IREG0 (when issuing INTBACK command)

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

IREG0: SMPC status acquisition switch setting value

IREG0 setting value	explanation
00H	date and time, cartridge code, area code, terminal status, SMEM, Do not return reset button data
01H	date and time, cartridge code, area code, terminal status, SMEM, Return each data of reset button

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

(2) When requesting continue or break

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

Figure 3.7 IREG0 (when requesting continue or break)

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

CONT	:Continue request bit ( if reversed , continues request)
BR	:Break request bit (If set to "1B" , break request)
−	: Either "1B" or "0B" is acceptable.

If a value that satisfies both CONT and BR requests is written to IREG0, SMPC cannot guarantee which operation will be executed. (See Table 3.2 )

●IREG1

IREG1 is used to set peripheral data acquisition mode.

●IREG1

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

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	return peripheral data

Bit 1: Optimization of peripheral data acquisition time

Bit 1	explanation
OPE
0	Optimize
1	no optimization

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

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: Undefined Write Only

When issuing the INTBACK command, be sure to set IREG2 to 0FH.