TI中文支持网Author: Jones Chen in Texas Instruments
1）JTAG pin
2）TRST
Do not use pull-up 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.)
3）Operations Mode Status Latched
The state of theTRST, EMU0, and EMU1 signals at device power up determine 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.
4）Test Program
A test program has been programmed, the program has been burn to flash in advance. The program toggles the GPIO34 which connected to LED3 to let the LED blink.
5）EMU0 and EMU1 Circuits:
6）XRST Circuit:
7）Experiment Description:
Emulator is disabled, so the TRST=0 when power on
Once power on, the four signals TRST XRST EMU0 EMU1 are monitored from the oscillograph.
1） The yellow line is the TRST signal
2） The aqua line is the XRST signal
3） The purple line is the EMU0 signal
4） The green line is the EMU1 signal
8）Operation mode:
9）Results:
|
Experiment Number |
Operation Mode entered |
Signals Description |
Program Run correctly |
Else |
|
1 |
Normal mode |
Figure 1 |
Yes, led blinking |
|
|
2 |
Wait in reset mode |
Figure 2 |
No |
|
|
3 |
Reserved for testing |
Figure 3 |
No |
|
|
4 |
Slave mode |
Figure 4 |
Yes, led blinking |
|
10）Figures:
【Figure 1】 Experiment 1, Power on moment（Normal Mode entered）
【Figure 2】 Experiment 2, Power on moment（Wait in reset modeentered）
【Figure 3】 Experiment 4, Power on moment（Reserved for testing mode entered）
【Figure 4】 Experiment 6, Power on moment（Slave mode entered）
