
DSP56321 Technical Data, Rev. 11
1-14
Freescale Semiconductor
Signals/Connections
1.11  JTAG and OnCE Interface
The DSP56300 family and in particular the DSP56321 support circuit-board test strategies based on the 
IEEE
 
Std. 
1149.1 test access port and boundary scan architecture, the industry standard developed under the 
sponsorship of the Test Technology Committee of IEEE and the JTAG. The OnCE module provides a means to 
interface nonintrusively with the DSP56300 core and its peripherals so that you can examine registers, memory, or 
on-chip peripherals. Functions of the OnCE module are provided through the JTAG TAP signals. For programming 
models, see the chapter on debugging support in the 
DSP56300 Family Manual
.
Table 1-15.     
JTAG/OnCE Interface
Signal
Name
Type
State During 
Reset
Signal Description
TCK
Input
Input
Test Clock
—A test clock input signal to synchronize the JTAG test logic.
TDI
Input
Input
Test Data Input
—A test data serial input signal for test instructions and data. 
TDI is sampled on the rising edge of TCK and has an internal pull-up resistor.
TDO
Output
Tri-stated
Test Data Output
—A test data serial output signal for test instructions and 
data. TDO is actively driven in the shift-IR and shift-DR controller states. TDO 
changes on the falling edge of TCK.
TMS
Input
Input
Test Mode Select
—Sequences the test controller’s state machine. TMS is 
sampled on the rising edge of TCK and has an internal pull-up resistor.
TRST
Input
Input
Test Reset
—Initializes the test controller asynchronously. TRST has an 
internal pull-up resistor. TRST must be asserted during and after power-up 
(see EB610/D for details).
DE
Input/ Output
Input
Debug Event
—As an input, initiates Debug mode from an external command 
controller, and, as an open-drain output, acknowledges that the chip has 
entered Debug mode. As an input, DE causes the DSP56300 core to finish 
executing the current instruction, save the instruction pipeline information, 
enter Debug mode, and wait for commands to be entered from the debug 
serial input line. This signal is asserted as an output for three clock cycles 
when the chip enters Debug mode as a result of a debug request or as a result 
of meeting a breakpoint condition. The DE has an internal pull-up resistor.
This signal is not a standard part of the JTAG TAP controller. The signal 
connects directly to the OnCE module to initiate debug mode directly or to 
provide a direct external indication that the chip has entered Debug mode. All 
other interface with the OnCE module must occur through the JTAG port.