GPIO
GPIO
22
22k
ECU
XETK-V2.0B
XETK
System
Controller
µC
22
1k
1k
22k
DAI1
DAI2
VCC_GPIO VCC_GPIO
XETK-V2.0 - User’s Guide
36
ETAS
Hardware Description
Fig. 4-18
Equivalent Circuitry of the XETK-V2.0B DAI Interface
To ensure proper operation of the startup protocol between ECU and XETK the
circuitry has to respect the following topics:
• 2 GPIO pins of the microcontroller are dedicated for the DAI functions,
referred to as DAI1 and DAI2
• 22 Ohm or similar value for matched impedance series resistors on each of
the DAI signals is recommended.
• 22 kOhm pull-up resistors on each of the DAI signals (refer to Fig. 4-18) is
required; internal CPU pull-up may be used.
• DAI1 and DAI2 must be tri-state or an input out of reset
• DAI1 and DAI2 must be configurable first as inputs and then as outputs
for the XETK-V2.0.
4.11.4
Phases of the Startup Protocol
During the startup phase the XETK and the ECU use a defined startup procedure.
This ensures the XETK does not access the ECU memory while it is being initial-
ized by the ECU software.
The DAI1 signal is dedicated to XETK detection, i.e. the XETK pulls DAI1 low
during the initial phases of the startup protocol. If no XETK is connected, DAI1
will be pulled weakly high via the 22 kOhm pull-up resistor on the ECU.
The DAI2 signal is dedicated to signal an ECU Standby power fail of the calibra-
tion RAM. DAI2 high indicates that a power failure occurred and that the calibra-
tion RAM content has not been restored by the XETK, while DAI2 low indicates
no power failure occurred.