◆Saturn Peripheral ID

●Saturn peripheral ID configuration

The Saturn peripheral ID consists of the peripheral type and data size. Saturn Peripheral ID allows you to recognize the configuration and content of peripheral data. Figure 3.15 shows the configuration of the Saturn peripheral ID.

Figure 3.15 Saturn peripheral ID configuration

bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
Sega Saturn Peripheral type				Data size

saturn peripheral type

Saturn Peripheral Type indicates the type of peripheral. Therefore, it can be used to recognize how peripheral data is ordered. Saturn currently defines four peripheral types and presents them in a standard format. See the Saturn Peripheral Standard Format section for more information.

Data size

The data size indicates how many bytes of peripheral data are output after the Saturn peripheral ID. Therefore, by using the data size, you can recognize how many bytes the peripheral data table consists of.
You can also recognize where the beginning of the data table for the next peripheral is.

●Details of Saturn Peripheral ID

＜ If a peripheral is connected directly to the peripheral port＞

Saturn peripherals define data sizes up to 255 bytes.
Saturn peripherals include peripherals with 15 bytes or less, and peripherals with 16 bytes or more and 255 bytes or less. There are also 15-byte mode and 255-byte mode for port mode. Therefore, there are four possible combinations of peripheral data size and port mode as shown in Table 3.8, and the configuration of Saturn peripheral ID and peripheral data is as shown in Figures 3.16 to 3.18.

Table 3.8 Peripheral data size and port mode combinations

(If a peripheral is connected directly to the peripheral port)

		Port mode (IREG1 setting)
		15	255
peripheral data Size [bytes]	15	Peripheral data configuration 1
	16-255	peripheral Data structure 2	peripheral Data structure 3

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Figure 3.16 Peripheral data configuration 1

saturn peripheral id	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
	0H～EH saturn peripheral type				1H～FH Data size

Peripheral data table	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
	Peripheral data 1st
	Peripheral data 2nd
	: : :
	peripheral data nth

nth is indicated by the data size and can be up to 15.

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Figure 3.17 Peripheral data configuration 2

saturn peripheral id	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
	0H～EH saturn peripheral type				0H Data size
Extended data size	0H				F0H

Peripheral data table	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
	Peripheral data 1st
	Peripheral data 2nd
	: : :
	peripheral data nth

Limit extended data size to 15 bytes.

Peripheral developers do not allow combinations in which the extended data size is 0FH when accessed in 255-byte mode.

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Figure 3.18 Peripheral data configuration 3

saturn peripheral id	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
	0H～EH saturn peripheral type				0H Data size
Extended data size	10H~FFH

Peripheral data table	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
	Peripheral data 1st
	Peripheral data 2nd
	: : :
	peripheral data nth

nth is indicated by the extended data size, with a maximum of n=255 .

＜ If a multi-tap is connected to the peripheral port＞

When connected to a multi-tap, the port mode indicates the maximum data size to collect from the peripherals connected to each tap. (This is not the total number of data collected from the entire multi-tap.)
If the connected peripheral is 15 bytes or less, it will be peripheral data configuration 1 regardless of whether the port mode is 15 byte mode or 255 byte mode.
If the connected peripheral is 16 bytes or more and the port mode is 15 byte mode, only up to 15 bytes will be collected as per peripheral data configuration 2.
If the connected peripheral is 16 bytes or more and the port mode is 255 byte mode, all data will be collected as per peripheral data configuration 3.
Also, if the specifications of the multi-tap itself is a maximum of 15 bytes for each tap, data of 16 bytes or more will be cut.
A mix of peripherals of 15 bytes or less and peripherals of 16 bytes or more may be connected to a multitap. However, when issuing the INTBACK command, the port mode can only be set to either 15 bytes or 255 bytes.
Therefore, the multi-tap specifications define the maximum data size that each tap can collect. When using multi-tap, set the port mode according to the maximum data size of the tap. In other words, if the multi-tap specification is a maximum of 15 bytes, set the port mode to 15-byte mode, and if the multi-tap specification is a maximum of 255 bytes, set the port mode to 255-byte mode.
The Saturn 6P multi-tap has a maximum of 15 bytes per tap. Use port mode in 15-byte mode.
Table 3.9 shows the combinations of multi-tap data size and port mode. Peripheral data configurations 1 to 3 in Table 3.9 are similar to those shown in Figures 3.16 to 3.18.
When using multi-tap, the connection status of each tap is indicated by the Saturn peripheral ID of each tap. When not connected to a tap or when an UNKNOWN device is connected to a tap, the Saturn peripheral ID is output in the configuration shown in Figure 3.19 and Figure 3.20.

Table 3.9 Peripheral data size and port mode combinations (multi-tap)

		Port mode (IRG1 setting)
		15	255
peripheral data Size [byte]	15	Peripheral data configuration 1
	16-255	peripheral Data structure 2	peripheral Data structure 3
	disconnected	Tap peripheral not connected
	UNKNOWN	tap peripheral UNKNOWN

Figure 3.19 Saturn peripheral ID when no peripheral is connected to the tap

saturn peripheral id	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
	FFH

Figure 3.20 Saturn peripheral ID when UNKNOWN peripheral is connected to tap

saturn peripheral id	bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
	FH saturn peripheral type				0H～EH Data size

Outputs the Mega Drive peripheral ID in the data size.

It can be treated in the same way as SMPC UNKNOWN.