Connections Between the Emulator and the Target System
15-10
15.7.2 Using a Target-System Clock
Figure 15–4 shows an application with the system test clock generated in the
target system. In this application, the TCK signal is left unconnected.
Figure 15–4. Target-System-Generated Test Clock
NC
System Test Clock
VCC
Emulator Header
GND
12
10
8
6
4
5
GND
GND
GND
GND
GND
PD
TCK_RET
TCK
TDO
TDI
TMS
TRST
EMU1
EMU0
9
11
7
3
1
2
14
13
JTAG Device
TCK
TDO
TDI
TMS
TRST
EMU1
EMU0
Greater Than
6 Inches
VCC
Note:
When the TMS/TDI lines are buffered, pullup resistors should be used to hold the buffer
inputs at a known level when the emulator cable is not connected.
There are two benefits to having the target system generate the test clock:
-
The emulator provides only a single 10.368-MHz test clock. If you allow
the target system to generate your test clock, you can set the frequency
to match your system requirements.
-
In some cases, you may have other devices in your system that require
a test clock when the emulator is not connected. The system test clock
also serves this purpose.