SEGA SATURN DEVELOPER'S MANUAL

SEGATAP is a 3-wire handshake peripheral. Sega Tap has two types of sequences: power-on reset and data request.

Power-on reset
When the power is turned on, the tap will automatically initialize. SEGATAP sets the TL bit to 0B during initialization and informs SH-2 that initialization is in progress.
Do not make a data request until initialization is complete.
Table 3.30 shows the data format for Sega Tap power-on reset in SH-2 direct mode.
Table 3.30 Data format at SEGA TAP power-on reset in SH-2 direct mode
Output force

Input force
TH
TR
TL
R
L
D
U
Resetting

1

1

0
0
0
0
0
Reset complete

1

1

1
0
0
0
0
Data request
This is a sequence to acquire data from SEGATAP.
∙ Start when TH is set to 0B, and end when both TH and TR are set to 1B.
The first data is the Mega Drive ID acquisition phase. Data can be obtained by changing TH from 1B to 0B. Read R, L, D, U after 2μS after TH change. Obtain the following data by handshaking with TR and TL.
Table 3.31 shows the data format when requesting Sega Tap data in SH-2 direct mode.