XETK-S4.2 - User’s Guide
23
ETAS
Hardware Description
4.8
JTAG Interface
Fig. 4-6
Equivalent Circuitry of the ECU JTAG Interface (ECU)
The ECU part of the JTAG XETK interface is depicted in Fig. 4-6. For proper oper-
ation it is mandatory for the ECU to provide series termination resistors of 22
Ohm in series with the /BRKOUT and TDO lines on the ECU PCB.
The XETK-S4.2 incorporates 22 Ohm series resistors for the TMS, TCK, TDI and /
TRST lines on the ECU interface. Hence, no additional termination resistors are
required on the ECU / debugger PCB for these signals.
It is mandatory for the ECU to provide impedance matched series termination
resistors of 22 Ohms for the signals TDO and /BRKOUT as shown in Fig 3-6.
Additionally, if a pulldown resistor is present on the line /TRST, the ECU must use
a value no smaller than 100K ohm as shown in Fig. 4-6 on page 23.
The signals /BRKIN and /BRKOUT pass through the XETK directly to the debug-
ger, with no connection to the XETK-S4.2 logic.
XETK
System
Controller
Micro -
controller
22
VCCIO
/BRKOUT
/BRKOUT
22
TDO
10k
TDO
/BRKIN
/BRKIN
VCCIO
10k
/TRST
10k
TDI
22
22
R >=100k
or Pullup
TDI
/TRST
TMS
TCK
TMS
22
22
1k
1k
TCK
ECU
XETK
