Nova Electronics MCX514, User Manual

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NOVA electronics Inc. MCX514 -
155
－ 155 －
4.2.1 Writing Operation
MCX514 Writing procedures to WR register are described below.
■
Generate start condition
When SCL signal is Hi and SDA signal changes from Hi to Low, it becomes start condition. Whenever sending and receiving, the
host CPU must generate this start condition at the beginning.
■
Write slave address
After making start condition, the user transmits an instruction whether to write from which WR register of which chip to MCX514.
It transmits 8-bit slave address synchronized with SCL shown below, and receives ACK (Low) from MCX514 in the 9th bit. The
slave address is composed of chip address of 3 bits D7
～
D5, register address of 4 bits D4
～
D1 and the bit D0 for reading /
writing.
SCL
SDA
1 2
3
4 5 6 7 8 9
CA2 CA1 CA0 RA3 RA2 RA1 RA0
Chip address Register address
ACK
Start
Condition
R/W
D7
D0 D5 D4 D1 D6 D3 D2
ACK: 0(Low) ； outputted by MCX514
Reading ： 1(Hi), Writing ： 0(Low)
Fig. 4.2-1 Slave Address
Specify the address set by A2 (22), A1 (23), A0 (24) pins of MCX514 to CA2
～
CA0 of chip address. Low is 0 and Hi is 1.
As for a register address, specify the register address that the user wants to write, referring to the following table. Although WR
register is 16-bit configuration, but I
2
C data transfer must be specified in bytes.
Table 4.2-1 Register Address for Writing
Register Address
WRn Register
RA3 RA2 RA1 RA0
0 0 0 0 WR0L
0 0 0 1 WR0H
0 0 1 0 WR1L
0 0 1 1 WR1H
0 1 0 0 WR2L
0 1 0 1 WR2H
0 1 1 0 WR3L
0 1 1 1 WR3H
1 0 0 0 WR4L
1 0 0 1 WR4H
1 0 1 0 WR5L
1 0 1 1 WR5H
1 1 0 0 WR6L
1 1 0 1 WR6H
1 1 1 0 WR7L
1 1 1 1 WR7H
WRnL is the low byte (D7
～
D0) of WRn.
WRnH is the high byte (D15
～
D8) of WRn.
The last bit D0 for writing of slave address is the bit to designate reading / writing. When writing, set it to 0..
If the slave address is sent by 8SCL, MCX514 returns ACK to SDA signal in the 9th SCL. When it receives 8-bit slave address
correctly, MCX514 corresponding to the chip address returns Low (open drain output is turned ON). When it is not received
correctly or the chip addresses do not match, not return Low.