L99MM70XP datasheet(24/68 Pages) STMICROELECTRONICS

24 / 68 page

Description

L99MM70XP

24/68

Doc ID 022637 Rev 2

Figure 7.

SPI global error information output

Chip Select Not (CSN)

The input pin is used to select the serial interface of this device. When CSN is high, the

output pin (DO) is in high impedance state. A low signal activates the output driver and a

serial communication can be started. The state during CSN = 0 is called a communication

frame.

Serial Data In (DI)

The input pin is used to transfer data serially into the device. The data applied to the DI are

sampled at the rising edge of the CLK signal and shifted into an internal 24 bit shift register.

At the rising edge of the CSN signal the contents of the shift register is transferred to data

input register. The writing to the selected data input register is only enabled if exactly 24 bits

are transmitted within one communication frame (i.e. CSN low). If more or less clock pulses

are counted within one frame the complete frame is ignored. This safety function is

implemented to avoid an activation of the output stages by a wrong communication frame.

Note:

Due to this safety functionality a daisy chaining of SPI is not possible. Instead, a parallel

operation of the SPI bus by controlling the CSN signal of the connected IC's is

recommended.

L99MM70XP Fiches technique(PDF) 24 Page - STMicroelectronics