SC18IS602B All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2017. All rights reserved.
Product data sheet Rev. 6 — 13 October 2017 7 of 26
NXP Semiconductors
SC18IS602B
I
2
C-bus to SPI bridge
the Function ID. There is no restriction on the number or combination of Slave Selects that
can be enabled for an SPI message. If more than one SSn
pin is enabled at one time, the
user should be aware of possible contention on the data outputs of the SPI slave devices.
The data on the SPI port will contain the same information as the I
2
C-bus data, but without
the slave address and Function ID. For example, if the message shown in Figure 6
is
transmitted on the I
2
C-bus, the SPI bus will send the message shown in Figure 7.
The SC18IS602B counts the number of data bytes sent to the I
2
C-bus port and will
automatically send this same number of bytes to the SPI bus. As the data is transmitted
from the MOSI pin, it is also read from the MISO pin and saved in the data buffer.
Therefore, the old data in the buffer is overwritten. The data in the buffer can then be read
back.
If the data from the SPI bus needs to be returned to the I
2
C-bus master, the process must
be completed by reading the data buffer. Section 8
gives an example of an SPI read.
7.1.4 Read from buffer
A read from the data buffer requires no Function ID. The slave address with the R/W bit
set to a ‘1’ will cause the SC18IS602B to send the buffer contents to the I
2
C-bus master.
The buffer contents are not modified during the read process.
A typical write and read from an SPI EEPROM is shown in Section 8.
Table 4. Function ID 01h to 0Fh
7 6 5 4 3 2 1 0
0000SS3SS2SS1SS0
Fig 6. I
2
C-bus message
Fig 7. SPI message
AS
002aac448
A P
FUNCTION
ID
WSLAVE ADDRESS
write to buffer
DATA 1
A A
DATA n
A
002aac451
SPI data
DATA 1
DATA n
Fig 8. Read from buffer
AS
002aac449
PR
SLAVE ADDRESS DATA 1
A A
DATA n
NA
