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RX - 8025 SA
NB
/
2
8.8.6. I
C bus's basic transfer format
• The write/read steps are illustrated below.
2
1) Write via I
C bus
• The steps for writing via the I
2
2) Read via I
C bus
(1) Standard read method for I
• The steps for standard reading of the I
(2) Simplified read method
• This RTC module also provides a special read method that uses fewer read steps.
(3) Read method from address Fh, with no specified start address for read operation
• Only when reading from address Fh (Fh → 0h → 1h → 2h, etc.) can a read operation be performed
without specifying the read start address or the transfer mode.
∗ The above steps are an example of transfers of one or two bytes only. There is no limit to the number of bytes
transferred during actual communications. (However, the transfer time must be no longer than 0.5 seconds and
access to the Address Dh (Reserved) register is prohibited.)
Master is transmitter (sending side),
RTC is receiver (receiving side)
Master is receiver (receiving side)､
RTC is transmitter (sending side)
2
C bus are shown below.
Slave address (7 bits)
S
Write
0
1
1
0
0
1
0
0
Slave address + write specification
2
C bus
Slave address (7 bits)
S
Write
0
1
1
0
0
1
0
0
Slave address + write specification
∗ This "write" is the writing of the read
start address, which occurs during a
read operation.
Slave address (7 bits)
Sr
Read
0
1
1
0
0
1
0
1
R
Slave address + read specification
e
∗ Indicates next byte will be read.
s
t
a
r
t
Slave address (7 bits)
S
Write
0
1
1
0
0
1
0
0
Slave address + write specification
∗ This "write" is the writing of the read
start address, which occurs during a
read operation.
Slave address (7 bits)
S
Read
0
1
1
0
0
1
0
1
Slave address + read specification
∗ Indicates next byte will be read.
START condition,
sent by Master
S
RESTART condition,
sent by Master
Sr
STOP condition,
sent by Master
P
Address setting
Transfer mode
A
0 h ∼ ∼ ∼ ∼ F h (∗ ∗ ∗ ∗ 1)
0 h (∗ ∗ ∗ ∗ 1)
Address + transfer mode specification
∗1) Specifies the write start address.
∗2) Specifies the write mode (= 0h fixed).
2
C bus are shown below.
Address setting
Transfer mode
A
0 h ∼ ∼ ∼ ∼ F h
0
0
0
0
Address and transfer mode settings
∗1) Specifies the read start address.
∗2) Specifies the Standard Read
mode (= 0h)
bit
bit
bit
bit
bit
bit
bit
bit
A
7
6
5
4
3
2
1
0
Data read (1)
∗ Data is read from the specified
start address.
Address setting
Transfer mode
A
0 h ∼ ∼ ∼ ∼ F h
0
1
0
0
Address and transfer mode settings
∗1) Specifies the read start address.
∗2) Specifies the Simplified
Read mode (= 4h)
bit
bit
bit
bit
bit
bit
bit
bit
7
6
5
4
3
2
1
0
Data read (1)
∗ Data is read from the specified
start address.
bit
bit
bit
bit
bit
bit
bit
bit
A
7
6
5
4
3
2
1
0
Data read (1)
∗ Since no address is specified, data is
read from address Fh.
Page - 26
Confirmation response from
Master
A
Master does not respond
/A
Confirmation response from
RTC
A
bit
bit
bit
bit
bit
bit
bit
bit
A
7
6
5
4
3
2
1
0
Write data
Standard Read mode
• Transfer mode setting = 0h
A
bit
bit
bit
bit
bit
bit
bit
bit
A
7
6
5
4
3
2
1
0
Data read (2)
∗ Address auto incrementation function
is used to add one to the last address
read to set the start address for the
next data to be read.
Simplified Read mode
• Transfer mode setting = 4h
A
bit
bit
bit
bit
bit
bit
bit
bit
A
7
6
5
4
3
2
1
0
Data read (2)
∗ Address auto incrementation function
is used to add one to the last address
read to set the start address for the
next data to be read.
bit
bit
bit
bit
bit
bit
bit
bit
A
7
6
5
4
3
2
1
0
Data read (2)
∗ The address auto incrementation
function is used to read data from
address Fh + 1 (= 0h).
ETM10E-04
A
P
/A
P
N
o
A
C
K
/A
P
N
o
A
C
K
/A
P
N
o
A
C
K
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