TLE7238GS

Serial Peripheral Interface (SPI)

Data Sheet

28

Rev. 1.0, 2008-10-30

CS Low to High transition:

•

Command decoding is only done, when after the falling edge of CS exactly a multiple (1, 2, 3, …) of eight SCLK

signals have been detected. In case of faulty transmission, the transmission error flag (TER) is set and the

command is ignored.

•

Data from shift register is transferred into the input matrix register.

SCLK - Serial Clock: This input pin clocks the internal shift register. The serial input (SI) transfers data into the

shift register on the falling edge of SCLK while the serial output (SO) shifts diagnostic information out on the rising

edge of the serial clock. It is essential that the SCLK pin is in low state whenever chip select CS makes any

transition.

SI - Serial Input: Serial input data bits are shifted in at this pin, the most significant bit first. SI information is read

on the falling edge of SCLK. The 8 bit input data consist of two parts (control and data). Please refer to Section 9.3

for further information.

SO Serial Output: Data is shifted out serially at this pin, the most significant bit first. SO is in high impedance state

until the CS pin goes to low state. New data will appear at the SO pin following the rising edge of SCLK. Please

refer to Section 9.3 for further information.

9.2

Daisy Chain Capability

The SPI of TLE7238GS 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 10),

which builds a chain. The ends 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.

Figure 10

Daisy Chain Configuration

In the SPI block of each device, there is one shift register where one bit from SI line is shifted in each SCLK. The

bit shifted out can be seen at SO. After 8 SCLK cycles, the data transfer for one device has been finished. In single

chip configuration, the CS line must go high to make the device accept the transferred data. In daisy chain

configuration the data shifted out at device #1 has been shifted in to device #2. When using three devices in daisy

chain, three times 8 bits have to be shifted through the devices. After that, the MCS line must go high (see

Figure 11).

SI

device 1

SPI

SO

SI

device 2

SPI

SO

SI

device 3

SPI

SO

MO

MI

MCS

MCLK

SPI_DasyChain.emf