RM0082
LS_I2C controller
Doc ID 018672 Rev 1
609/844
Figure 62.
START and STOP conditions [from I
2
C-bus specification]
Addressing slave protocol
Two address formats are supported: the 7 bit address format and the 10 bit address format.
In case of the 7 bit address format, the first seven bits (bits 7 to 1) of the first byte sent on the
bus after the START condition set the slave address, while the LSB is the data direction bit.
In particular, if LSB is set to ‘b0, the master writes to the slave (WRITE operation), otherwise
(LSB set to ‘b1) the master reads from the slave (READ operation). Data is transmitted from
the MSB.
In case of 10 bit addressing, two bytes are transferred following a START condition to set the
10 bit address. The first five bits (7 to 3) notify the slaves that this is a 10 bit transfer,
followed by the next two bits (2 to 1) which set the bit 9 and 8 of the 10 bit slave address.
The LSB of the first byte is the RW bit.
lists the special purpose and reserved first
byte addresses. The second byte transferred sets bits 7 to 0 of the 10 bit slave address.
Table 538.
First byte assignment in addressing slave protocol
First byte sent
Description
BIT [7:1]
RW BIT [0]
7’b0000 000
1‘h0
General call address. The I
2
C controller places the data in
the receive buffer and issues a general call interrupt
(
).
7’b0000 000
1‘h1
START byte
(see Section: START byte transfer
protocol)
.
7’h0000 001
1’hX
CBUS address. The I
2
C controller ignores these accesses.
7’h0000 010
1’hX
Reserved.
7’h0000 011
1’hX
Reserved.
7’h0000 1XX
1’hX
High-speed master code.
7’h1111 1XX
1’hX
Reserved.
7’h1111 0XX
1’hX
10 bit slave addressing.
SDA
SCL
S
P
START Condition
STOP Condition