Designing Your Target System’s Emulator Connector (14-Pin Header)
15-2
15.1 Designing Your Target System’s Emulator Connector (14-Pin Header)
JTAG target devices support emulation through a dedicated emulation port.
This port is a superset of the IEEE 1149.1 standard and is accessed by the
emulator. To communicate with the emulator, your target system must have
a 14-pin header (two rows of seven pins) with the connections that are shown
in Figure 15–1. Table 15–1 describes the emulation signals.
Figure 15–1. 14-Pin Header Signals and Header Dimensions
TDO
7
8
GND
TMS
1
2
TRST
TDI
3
4
GND
TCK_RET
9
10
GND
TCK
11
12
GND
Header Dimensions:
Pin-to-pin spacing, 0.100 in. (X,Y)
Pin width, 0.025-in. square post
Pin length, 0.235-in. nominal
PD (V
CC
)
5
6
no pin (key)
†
EMU0
13
14
EMU1
† While the corresponding female position on the cable connector is plugged to prevent improper
connection, the cable lead for
pin 6 is present in the cable and is grounded, as shown in the sche-
matics and wiring diagrams in this document.
Table 15–1. 14-Pin Header Signal Descriptions
Signal
Description
Emulator
†
State
Target
†
State
TMS
Test mode select
O
I
TDI
Test data input
O
I
TDO
Test data output
I
O
TCK
Test clock. TCK is a 10.368-MHz clock
source from the emulation cable pod. This
signal can be used to drive the system test
clock
O
I
TRST
‡
Test reset
O
I
EMU0
Emulation pin 0
I
I/O
EMU1
Emulation pin 1
I
I/O
PD(V
CC
)
Presence detect. Indicates that the emula-
tion cable is connected and that the target is
powered up. PD should be tied to V
CC
in the
target system.
I
O
TCK_RET
Test clock return. Test clock input to the
emulator. May be a buffered or unbuffered
version of TCK.
I
O
GND
Ground
† I = input; O = output
‡ Do not use pullup resistors on TRST: it has an internal pulldown device. In a low-noise
environment, TRST can be left floating. In a high-noise environment, an additional pulldown
resistor may be needed. (The size of this resistor should be based on electrical current
considerations.)