7220 Datasheet, PDF (205/303 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
5.5 Example of I²C-BUS control by software (M37220M3-XXXSP/FP)
(7) Data input processing routine
Data intput
Bit 0 of port P2 direction register
= “input mode”
“BIT COUNTER” = “0”
RAM: READDATA
BIT COUNTER
P21 (SCL) = “1”
Wait 6 µs
No
P20 (SDA) = “1”?
Yes
Carry flag = “1”
Rotate “READDATA”
with Carry flag, to left
P21 (SCL) = “1”
“BIT COUNTER”
←“BIT COUNTER” + 1
Carry flag = “0”
No
“BIT COUNTER”
≥ “8”?
Yes
RETURN
Fig. 5.5.10 Flowchart of data input processing routine
5-32
7220 Group User’s Manual