Pin Header Signal Descriptions - Texas Instruments TMS320C28x Reference Manual

Debug Interface
Table 7−1. 14-Pin Header Signal Descriptions
7-4
Signal Description
EMU0 Emulation pin 0
EMU1 Emulation pin 1
GND Ground
PD (V ) Presence detect. Indicates that the emulation
CC
cable is connected and that the target is pow-
ered up. PD should be tied to V
system.
TCK Test clock. TCK is a clock source from the
emulation cable pod. This signal can be used
to drive the system test clock.
TCK_RET Test clock return. Test clock input to the emu-
lator. Can be a buffered or unbuffered version
of TCK.
TDI Test data input
TDO Test data output
TMS Test mode select
TRST ‡ Test reset
†
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.)
The state of the TRST, EMU0, and EMU1 signals at device power up deter-
mine the operating mode of the device. The operating mode takes effect as
soon as the device has sufficient power to operate. Should the TRST signal
rise, the EMU0 and EMU1 signals are sampled on its rising edge and the\at
operating mode is latched. Some of these modes are reserved for test pur-
poses, but those that can be of use in a target system are detailed in Table 7−2.
A target system is not required to support any mode other than normal mode.
Emulator
State †
I
I
I
in the target
CC
O
I
O
I
O
O
Target
State †
I/O
I/O
O
I
O
I
O
I
I