Datasheet

Emulation Signals
3-2
3.1 Emulation Signals
There are five standard signals and a ground used for JTAG connections to
control the JTAG
†
Test Access Port (TAP) Controller, as defined by the IEEE
1149.1 standard.
These signals are shown in Table 3−1.
As a method of confirming a proper connection of the emulation hardware, TI
also uses two other signals provided on the JTAG header (Table 3−2):
- The Target Voltage Detect signal
- The Target Disconnect signal
The Target Voltage Detect signal is used to set the I/O voltage of the XDS560
Target pod. The Target Disconnect signal should be tied to ground on the target
board.
†
The term JTAG, as used in this book, refers to TI scan-based emulation, which is based on the IEEE 1149.1 standard.
Table 3−1. Standard TAP Controller JTAG Signals
Signal
Name
Description
Emulator
Signal Type
†
Target
Signal Type
‡
TRST‡ Test Reset‡ O I
TMS Test Mode Select O I
TDI Test Data Input O I
TDO Test Data Output I O
TCK Test Clock (XDS560 POD sourced) O I
TCK_RET Test Clock Return (Buffered or un-buffered connection of
TCK coming back from the target)
IO
GND
Ground GND
†
I = Input, O = Output
‡
Do not use pullup resistors on TRST: it has an internal pull-down device. In a low-noise environment, TRST can be left floating.
In a high-noise environment, an additional pull-down resistor may be needed. (The size of this resistor should be based on
electrical current considerations.)
Table 3−2. XDS560 Connection Signals
Signal
Name
Description
Emulator
Signal Type
†
Target
Signal Type
TVD(V
I/O
) Target Voltage Detect: TVD should be tied to the I/O Volt-
age of the target processor.
I O
TDIS Target Disconnect I GND
†
I = Input, O = Output