MLX16303 Datasheet, PDF (12/20 Pages) Melexis Microelectronic Systems – Bi-directional Remote Sensor Unit Interface

MLX16303
Bi-directional Remote Sensor Unit Interface
logical high at SSIOx, OUTx switches to high voltage level and vice versa. The SSIOx pins must have
internal pull down 50kOhm (tolerance +/- 20%) resistors
Data transmission to the remote unit
It is possible to send data to the remote units. For this the OUTx voltage can be modulated by the bi-
directional remote unit interface IC between two defined voltage ranges (high and low) using the pins
SSIOx. The low level is the default level. This programming mode is enabled and disabled with an SPI
command. The data transfer to the satellite is only possible in an limited battery range, otherwise a failure
flag via SPI will be sent to microcontroller.
Data transmission from the remote unit
The data transmission from the external remote units to the bi-directional remote unit interface IC is done
by varying the current level.
The quiescent current consumption of the external remote units is interpreted as logic high level at SSIOx
pin. This means the SSIOx output drives the high level if the quiescent current consumption is sensed at
the according OUTx pin. The remote units can switch on an additional fixed current, interpreted by the
interface as logic low level at SSIOx. The SSIOx pins are CMOS-compatible and can be connected
directly to a microcontroller.
SPI (Serial Parallel Interface)
The bi-directional remote unit IC is always the slave and the microcontroller the master of the 16bit serial
parallel interface (SPI).
Data transfer timing
The standard SPI needs four CMOS-compatible pins.
The data input DI, the data output DO, the clock CLK and the chip select CS. The communication starts
after the H-L edge of the CS signal (low active).
The DI and DO signals are synchronized with CLK(CLK idle is low).
The DI signal is latched from the data bus to an internal shift register with the falling edge of the CLK
signal. The DO signal is shifted from an internal shift register to the data bus with the rising edge. The
data output DO is in tri-state mode when the CS signal is high. The CS will be deactivated after each
command. CLK is only active when CS is set to low level. MLX16303 has to monitor the exact number of
CLK-pulses by counting them. The answer after the first command must be the answer of the NOP-
command.
Communication protocol
The IC gets 16bit data from the microcontroller via SPI. The bit 0 - 2 will be interpreted as a command.
The other bits are data.
When a command word is sent to the MLX16303 the first bit on the data bus must be bit0 (LSB) followed
by the bits 1-15. The first bit of the answer word from MLX16303 must be bit0 followed by the bits 1-15.
After transmission of a command with one command delay an ‘answer word’ is sent by MLX16303. If a
command word matches completely with the known possible commands the respective action has to be
done. The command word is fully reflected except for the bits that contain useful information in the
command word.
If a sent SPI command is not a defined one all bits in the regarding answer word must be set to ‘1’.
3901016303
Rev. 004
Page 12 of 20
Data Sheet
Jun/04