External Core Complex Interfaces
e200z3 Power Architecture Core Reference Manual, Rev. 2
Freescale Semiconductor
7-7
7.3
Signal Descriptions
describes the processor clock, m_clk.
describes signals that are related to reset. The core supports several reset input signals for the
CPU and JTAG/OnCE control logic: m_por, p_reset_b, and j_trst_b. The reset domains are partitioned
such that the CPU p_reset_b signal does not affect JTAG/OnCE logic and j_trst_b does not affect
processor logic. It is possible and desirable to access OnCE registers while the processor is running or in
reset. It is also possible and desirable to assert j_trst_b and clear the JTAG/OnCE logic without affecting
the processor state.
The synchronization logic between the processor and debug module requires an assertion of either j_trst_b
or m_por during initial processor power-on reset to ensure proper operation. If the pin associated with
j_trst_b is designed with a pull-up resistor and left floating, assertion of m_por is required during the initial
power-on processor reset. Similarly, for those systems that do not have a power-on reset circuit and choose
to tie m_por low, it is required to assert j_trst_b during processor power-up reset. When a power-up reset
is achieved, the two resets can be asserted independently.
A reset output signal, p_resetout_b, is also provided.
j_shift_ir
O
0
Shift_IR state of JTAG controller
j_capture_dr
O
0
Parallel test data register load state of JTAG controller
j_shift_dr
O
0
TAP controller in shift DR state
j_update_gp_reg
O
0
Updates JTAG controller test data register
j_rti
O
0
JTAG controller run-test-idle state
j_key_in
I
Input for providing data to be shifted out during shift_IR state when
jd_en_once is
negated
j_en_once_regsel
O
0
External enable OnCE register select
j_nexus_regsel
O
0
External Nexus register select
j_lsrl_regsel
O
0
External LSRL register select
j_gp_regsel[0:11]
O
0
General-purpose external JTAG register select
j_id_sequence[0:1]
I
JTAG ID register (2 msbs of sequence field)
j_id_version[0:3]
I
JTAG ID register version field
j_serial_data
I
Serial data from external JTAG registers
Table 7-2. Processor Clock Signal Description
Signal I/O
Signal Description
m_clk
I
Processor clock. The synchronous clock source for the core. Because the core is designed for static
operation,
m_clk can be gated off to lower power dissipation (for example, during low-power stopped
states).
Table 7-1. Interface Signal Definitions (continued)
Signal Name
I/O Reset
Definition
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