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3.2
Programming Interface
3.2.1
Communication Scheme
The digital programming interface uses specific frames, which can have one of the two following functions:
•
Command frames contain a specific task (e.g. read/write data, select EEPROM programming etc.) and a
corresponding address
•
Data frames contain a 16 bit data value sent to or received from the device - these frames can only follow a
proper command frame for reading or writing data
A valid frame has the following properties:
•
A frame consists of 21 bits in total
•
A bit is shifted in or out via the output line with a rising clock edge on the supply line
•
A frame always starts and ends with a '1' (frame bits)
•
The LSB of a frame transmitted to the sensor is shifted in first
•
The LSB of a frame replied by the sensor is shifted out first
•
The whole frame sent to the device, including frame bits, is protected with an even positional and an odd
positional parity bit
The first frame sent has to be a valid command to activate the interface mode and it has to be sent within 19ms
after power up. As an additional protection, the device does not deactivate its output stage during this transmission
(using 21 clock pulses) as shown in
overrule the open drain output stage of the sensor during this initial transmission.
power up
Figure 3-2 First Frame Transmission to the Sensor
Attention: Overruling Vout requires a strong driver on the programmer, since the OUT line must be driven
to low levels close to GND for any "0"-bit and close to VDD for any "1"-bit in order to ensure a
proper communication with the sensor.
After the first frame, to avoid additional power consumption in the output stage of the device, the internal driver is
deactivated in programming mode while the sensor is receiving a frame. It is activated again after completion of
the transmission. This is illustrated in
leading driver
off pulse
interface
active
protocol
output
internal buffer on
Figure 3-3 Further Frame Transmisson from the Programmer to the Sensor (Write Access)
User's Manual
Figure
3-2. This means that the interface driver of the programmer needs to
LSB
during first transmission, the output stage is still switched on
Figure
3-3.
Z
LSB
during transmission the buffer is switched off
VDD
Vout
VDD
Vout
6
User's Manual
TLE4997 Programming
interface
activated
MSB
interface
active
protocol
MSB
output
internal buffer on
v01_01, 2019-08
TLE4997
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