7220 Datasheet, PDF (202/303 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

APPLICATION
5.5 Example of I²C-BUS control by software (M37220M3-XXXSP/FP)
(2) Read processing routine
Œ

Ž


Slave address ^A
S _{(W) “A016”}
C
K
Sub-address
A
C
R
KS
Slave address
(R) “A116”
A
C
K
Read start
‘
Data
’“
(See note 1)
N
A
C
P
K
RAM: WRITEDATA
NO ACK COUNTER
READ DATA COUNTER
Flag: F_ACK
To M52340SP ?
(See note 2)
No (to other devices (cf. E ²PROM))
Yes (sub-address is not necessary at reading)
“WRITEDATA”
←Slave address (W) “A0 16”
“NO ACK COUNTER” = “0”
START condition
Œ
Data output

No (no ACK)
“F_ACK” = “0”?
Yes (ACK)
“WRITEDATA” ←Sub-address
Data output
Ž
No (no ACK)
“F_ACK” = “0”?
Yes (ACK)
START condition

“WRITEDATA”
←Slave address (R) “A1 16”
Data output
No (no ACK)
“F_ACK” = “0”?
Yes (ACK)
Data input
STOP condition
“NO ACK COUNTER”
←“NO ACK COUNTER” + 1
“READ DATA
COUNTER” = “0”?
Yes (end)
“NO ACK COUNTER”
No (try 3 times) ^{≥ “3”?}
Yes (give up)
Return NACK
STOP condition

Notes 1: NACK = No ACK
2: Branches according to whether the
device needs sub-address or not.
‘
No (not yet)
’
“
Return ACK
Bus H
End
Fig. 5.5.5 Flowchart of read processing routine
“READ DATA COUNTER”
←“READ DATA COUNTER” – 1
7220 Group User’s Manual
5-29