JTAG Emulator Cable Pod Logic
15-4
15.4 JTAG Emulator Cable Pod Logic
Figure 15–2 shows a portion of the emulator cable pod. These are the func-
tional features of the pod:
-
Signals TDO and TCK_RET can be parallel-terminated inside the pod if
required by the application. By default, these signals are not terminated.
-
Signal TCK is driven with a 74LVT240 device. Because of the high-current
drive (32 mA I
OL
/I
OH
), this signal can be parallel-terminated. If TCK is tied
to TCK_RET, then you can use the parallel terminator in the pod.
-
Signals TMS and TDI can be generated from the falling edge of TCK_RET,
according to the IEEE 1149.1 bus slave device timing rules.
-
Signals TMS and TDI are series-terminated to reduce signal reflections.
-
A 10.368-MHz test clock source is provided. You may also provide your
own test clock for greater flexibility.
Figure 15–2. JTAG Emulator Cable Pod Interface
100
Ω
TL7705A
RESIN
270
Ω
JP2
180
Ω
TCK_RET (Pin 9)
{
EMU1 (Pin 14)
EMU0 (Pin 13)
74AS1034
GND (Pins 4,6,8,10,12)
TRST (Pin 2)
TCK (Pin 11)
{
10.368 MHz
33
Ω
33
Ω
TDI (Pin 3)
TMS (Pin 1)
TDO (Pin 7)
74LVT240
180
Ω
JP1
270
Ω
74F175
Q
Q
D
PD(VCC) (Pin 5)
+5 V
+5 V
74AS1004
Y
Y
Y
Y
A
† The emulator pod uses TCK_RET as its clock source for internal synchronization. TCK is provided
as an optional target system test clock source.