◆ Result parameter of INTBACK command

This section describes the result parameters for acquiring peripheral data using the INTBACK command.

● Basic configuration of result parameters obtained by INTBACK command

The INTBACK command configures the result parameters shown in Figure 3.10 in the status register and OREG.
Peripheral control status shows various statuses in peripheral control mode. The port 1 status and port 2 status show the peripheral connection status of each port. The ID and peripheral data of the connected peripheral are output to the port 1 data and port 2 data. When the peripheral is directly connected to the peripheral port, the peripheral data for one unit is output. Also, when multi-tap is connected, peripheral data for the number of taps is output.

Figure 3.10 Basic configuration of result parameters obtained by INTBACK command

┌───────────┐ ┌─────┬─────┬─────┬─────┬─────┬─────┬ ─────┐　
SR │ Peripheral │ = │ 1 │ PDL │ RESB │ P2MD1 │ P2MD0 │ P1MD1 │ P1MD0 │　
│ Control status │ └─────┴─────┴─────┴─────┴─────┴─────┴─────┘　
├───────────┤───┌──────────┐ ┌────────┬────────┐　
│ │ │ Port 1 status │ ＝ │ Multi-tap ID │ Number of connectors │　
│ │ ├──────────┤ └────────┴────────┘　
│ Port 1 data │ │ Peripheral 1 data │　
│ │ ├──────────┤───┌──────────────┐┌─────────┬────── ───┐
│ │ │ Peripheral 2 data │ │ Saturn Peripheral ID │ = │ Sega Saturn │ Data size │
OREG ├────────┤─┐├──────────┤─┐├──────────────┤ │ Peripheral type │ │
│ │ │ │ ： │ │ │ Extended data size │ └─────────┴─────────┘
│ │ │ ├──────────┤ │ ├──────────────┤　
│ Port 2 data │ │ │: │ │ │ Peripheral 2 1st data │　
│ │ │ ├──────────┤ │ ├──────────────┤　
│ │ │ │ ： │ │ │ Peripheral 2 2nd data │　
└───────────┘ │ ├──────────┤ │ ├──────────────┤　
│ │: │ │ │ │: │　
│ ├──────────┤ │ ├──────────────┤　
│ │ Peripheral m data │ │ │ │: │　
└─└──────────┘ │ ├──────────────┤　
│ │: │　
│ ├──────────────┤　
│ │ Peripheral 2nd data │　
└─└──────────────┘　

● Result parameter configuration in 0-byte mode

If either port is set to 0-byte mode, the data of the port set to 0-byte mode will be lost and the structure will be packed.
Figure 3.11 shows the data structure when one is in 0-byte mode.

Figure 3.11 Result parameter configuration when one is in 0-byte mode

As described above, the configuration of the result parameter differs depending on the command parameter setting conditions. Table 3.4 shows the relationship between the command parameter setting conditions and the generated result parameter configuration.

Table 3.4 Command parameter setting conditions and peripheral data structure

Command parameter setting conditions				Result parameter configuration
Returns SMPC status	Returns peripheral data	With port 1 control	With port 2 control	SMPC status	Port 1 data	Port 2 data
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