
8-48
G2 PowerPC Core Reference Manual
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MOTOROLA
Signal Descriptions
Figure 8-4. IEEE 1149.1-Compliant Boundary Scan Interface
These signals are not used during normal operation. core_tms, core_tdi, and core_trst have
internal pull-up resistors provided; core_tck does not. For normal operation, core_tms and
core_tdi may be left unconnected, and core_tck must be set high or low. The core_trst signal
must be asserted sometime during power-up for JTAG logic initialization. Note that if
core_trst is tied low, unnecessary power is consumed.
8.3.12.1 JTAG Test Clock (core_tck)—Input
The JTAG test clock (core_tck) signal is an input on the G2 core. Following are the state
meaning and timing comments for the core_tck input signal.
State Meaning
Asserted/Negated—This input should be driven by a free-running
clock signal. Input signals to the test access port are clocked in on the
rising edge of core_tck. Changes to the test access port output signals
occur on the falling edge of core_tck. The test logic allows core_tck
to be stopped.
Timing Comments
Assertion/Negation—core_tck should not be used during normal
operation and always must be set to either a high or low logic state.
8.3.12.2 JTAG Test Data Input (core_tdi)—Input
Following is the state meaning and timing comments for the core_tdi input signal.
State Meaning
Asserted/Negated—The value presented on this signal on the rising
edge of core_tck is clocked into the selected JTAG test instruction or
data register.
Timing Comments
Assertion/Negation—core_tdi should not be used during normal
operation and always must be set to a high or low logic state. Note
that this input contains an internal pull-up resistor to ensure that an
unterminated input appears as a high signal level to the test logic.
core_tdi
(Test Data Input)
core_tms
(Test Mode Select)
core_tck
(Test Clock Input)
core_TDO
(Test Data Output)
core_trst
(Test Reset)
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