TLE8108EM Datasheet, PDF (23/30 Pages) Infineon Technologies AG – Smart 8-Channel Low Side Relay Driver with SPI Interface

TLE 8108 EM
Smart 8-Channel Low Side Switch
Serial Peripheral Interface (SPI)
8.2
Daisy Chain Capability
The SPI of TLE8108EM provides daisy chain capability. In this configuration several devices are activated by the
same CS signal (MCS). The SI line of one device is connected with the SO line of another device (see Figure 12),
to build a chain. The terminations of the chain are connected with the output and input of the master device, MO
and MI respectively. The master device provides the master clock MCLK, which is connected to the SCLK line of
each device in the chain.
Slave 1
Slave 2
Slave 3
MO
SI
SO
SI
SO
SI
SO
SCLK
SPI
CS
SCLK
SPI
CS
SCLK
SPI
CS
MCLK
MCS
MI
Figure 12 Daisy Chain Configuration
SPI Daisy Chain.vsd
In the SPI block of each device, there is a shift register where one bit from SI line is shifted at each SCLK. The bit
shifted out can be seen at SO. After 16 SCLK cycles, the data transfer for one TLE8108EM has been finished. In
single chip configuration, the CS line must go high to make the device accepting the transferred data. In daisy
chain configuration the data shifted out at device #1 is shifted in at device #2. When using multiple devices in daisy
chain, the number of transferred bits must correspond to the number of the register bits of all chained devices.
Figure 13 shows an example with 3 SPI devices, where #1 and #3 are 16-bit SPI and #2 has a 8-bit SPI. To get
a successful transmission, there must be (2*16 + 1*8)-bit shifted through the devices. After that, the MCS line can
go high.
MI
MO
MCS
MCLK
SO device 3
SI device 3
SO device 2
SI device 2
Figure 13 Data Transfer in Daisy Chain Configuration
SO device 1
SI device 1
t
SPI Daisy Chain data Transfer.vsd
Data Sheet
23
Rev. 1.0, 2011-03-23