NCT210
http://onsemi.com
11
before the 10th clock pulse, then high during the
10th clock pulse to assert a stop condition.
Any number of bytes of data can be transferred over the
serial bus in one operation, but it is not possible to mix read
and write in one operation, because the type of operation is
determined at the beginning and cannot subsequently be
changed without starting a new operation.
For the NCT210, write operations contain either one or
two bytes, while read operations contain one byte.
To write data to one of the device data registers or read
data from it, the address pointer register must be set so that
the correct data register is addressed, data can then be written
into that register or read from it. The first byte of a write
operation always contains a valid address that is stored in the
address pointer register. If data is to be written to the device,
the write operation contains a second data byte that is written
to the register selected by the address pointer register.
This is illustrated in Figure 13. The device address is sent
over the bus followed by R/W
set to 0. This is followed by
two data bytes. The first data byte is the address of the
internal data register to be written to, which is stored in the
address pointer register. The second data byte is the data to
be written to the internal data register.
Figure 13. Writing a Register Address to the Address Pointer Register, then Writing Data to the Selected Register
A6
SCLK
SDATA
A5   A4    A3   A2    A1    A0
D7    D6   D5   D4    D3   D2    D1    D0
ACK. BY
NCT210
START BY
MASTER
1
9
1
ACK. BY
NCT210
9
D7    D6    D5   D4    D3   D2    D1    D0
ACK. BY
NCT210
STOP BY
MASTER
1
9
SCLK (CONTINUED)
SDATA (CONTINUED)
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
FRAME 3
DATA BYTE
R/W
Figure 14. Writing to the Address Pointer Register Only
A6
SCLK
SDATA
A5    A4
A3
A2
A1
A0
D7    D6
D5
D4    D3    D2    D1
D0
ACK. BY
NCT210
STOP BY
MASTER
START BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
ADDRESS POINTER REGISTER BYTE
1
1
9
ACK. BY
NCT210
9
R/W
Figure 15. Reading Data from a Previously Selected Register
A6
SCLK
SDATA
A5   A4    A3    A2    A1    A0
D7    D6    D5    D4    D3    D2    D1    D0
NO ACK. BY
MASTER
STOP BY
MASTER
START BY
MASTER
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
DATA BYTE FROM NCT210
1
1
9
ACK. BY
NCT210
9
R/W
When reading data from a register there are two
possibilities:
1. If the NCT210s address pointer register value is
unknown or not the desired value, it is first
necessary to set it to the correct value before data
can be read from the desired data register. This is
done by performing a write to the NCT210 as
before, but only the data byte containing the
register read address is sent, because data is not to
be written to the register. This is shown in
Figure 14.
A read operation is then performed consisting of
the serial bus address, R/W
bit set to 1, followed