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5-28

APPLICATION

5.5 Example of I2C-BUS control by software (M37220M3-XXXSP/FP)

7220 Group User’s Manual

5.5.4 General flowchart

(1)

Write processing routine

The processing routine which controls I2C-BUS devices branch to the write processing routine and

the read processing routine. The START condition, the STOP condition and the data output processing

routine are used as the common processing routine.

Fig. 5.5.4 Flowchart of write processing routine

Write start

“WRITEDATA”

←Slave address (W) “BA 16”

“F_ACK” = “0”?

Data output

Yes (ACK)

RAM:

Flag:

WRITEDATA

NO ACK COUNTER

WRITE DATA COUNTER

F_ACK

Slave address

(W) “BA16”

Sub-address

Data

“WRITE DATA COUNTER”

“NO ACK COUNTER” = “0”

START condition

“WRITEDATA”

←Sub-address

“F_ACK” = “0”?

Yes (ACK)

No (no ACK)

“WRITE DATA

COUNTER” = “0”?

Yes (end)

No (not yet)

“NO ACK COUNTER”

←“NO ACK COUNTER” + 1

End

STOP condition

Bus H

Data output

“WRITEDATA”

←Write data

“WRITE DATA COUNTER”

←“WRITE DATA COUNTER” – 1

STOP condition

“NO ACK COUNTER”

≥ “3”?

Yes (give up)

No (try 3 times)

= “1” (number of write bytes)

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