Analog Integrated Circuit Device Data

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Freescale Semiconductor

21

33814

5.1.6

GND

both the power supplies as well as power ground for some of the lower current output drivers. The higher current output drivers

have their own ground pins. All ground pins (INJGND1, INJGND2, RGND1, and RGND2) and the exposed pad must be directly

connected to this pin and the negative battery terminal. There is no separate ground pin associated with the LAMPOUT driver,

it shares a ground with ROUT2.

5.1.7

SCLK Input

The serial clock (SCLK) pin clocks the internal SPI shift register of the 33814. The SI data is latched into the input shift register

on the rising edge of SCLK signal. The SO pin shifts status bits out on the falling edge of SCLK. The SO data is available for the

MCU to read on the rising edge of SCLK. With CSB in a logic high state, signals on the SCLK and SI pins will be ignored and the

SO pin will be in a high-impedance state.The SCLK signal consists of a 50% duty cycle with CMOS logic levels referenced to

of CSB going low and then high, a SPI error is reported in the SPI Status Register. The SPI error bit will also be set whenever

an invalid SPI message is received, even though it may contain 16-bits.

5.1.8

CSB Input

The system MCU selects which slave is to receive SPI communication using separate chip select (CSB) pins. With the CSB in a

logic low state, SPI words may be sent to the 33814 via the serial input (SI) pin, and status information is received by the MCU

via the serial output (SO) pin. The falling edge of CSB enables the SO output and transfers status information into the SO buffer.

The rising edge of the CSB initiates the following operation:

1. Disables the SO driver (high-impedance)

2. Activates the received command word, allowing the 33814 to activate/deactivate output drivers.

To avoid any spurious data, it is essential that the high-to-low and low-to-high transitions of the CSB signal occur only when SCLK

5.1.9

SI Input

The SI pin is used for serial instruction data input. SI information is latched into the input register on the rising edge of SCLK and

the input data transitions on the falling edge of SCLK. A logic high state present on SI will program a one in the command word

on the rising edge of the CSB signal. To program a complete word, 16 bits of information must be entered into the device.This

5.1.10 SO Output

The SO pin is the output from the SPI shift register. The SO pin remains high-impedance until the CSB pin transitions to a logic

low state. All normal operating drivers are reported as zero, all faulted drivers are reported as one. The negative transition of CSB

enables the SO driver.

The SI/SO shifting of the data follows a first-in-first-out protocol, with both input and output words transferring the most significant

bit (MSB) first.

The serial output data is available to be latched by the MCU on the rising edge of SCLK. The SO data transitions on falling edge