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External Core Complex Interfaces
e200z3 Power Architecture Core Reference Manual, Rev. 2
7-28
Freescale Semiconductor
shows an example for designing an external JTAG register set using the inputs and outputs
provided along with the JTAG primary inputs. The main components are a clock generation unit, a JTAG
shifter (load, shift, hold, clr), the registers (load, hold, clr), and an input mux to the shifter for the serial
output back to the core.The shifter and the registers may be as wide as the application warrants [0:x]. The
length determines the number of states the TAP controller is held in Shift_DR (x+1).
Figure 7-2. Example External JTAG Register Design
j_serial_data
I
Serial data. Receives serial data from external JTAG registers. All external registers share this serial
output back to the core. Therefore it must be muxed using
j_gp_regsel[0:11], j_lsrl_regsel, and
j_en_once_regsel. The data is internally routed to j_tdo.
j_key_in
I
Key data in. Receives serial data from logic to indicate a key or other value to be scanned out in the
Shift_IR state when the current value in the IR is the Enable_OnCE instruction. This input is provided
to assist in implementing security logic outside of the core, which conditionally asserts
jd_en_once.
During the Shift_IR state, when
jd_en_once is negated, this input is sampled on the rising edge of
j_tclk, and, after a 2-clock delay, the data is internally routed to j_tdo. This allows provision of a key
value via the
j_tdo output following a transition from Capture_IR to Shift_IR. j_key_in provides the key
value.
Table 7-22. Descriptions of JTAG Interface Signals (continued)
Signal
I/O
Signal Description
Shifter
D
Data
Q
REG0
Q
D
REG1
Q
j_gp_regsel[1:0]
S
D
0
1
reg0_dat
reg1_dat
clk_reg0
2
clk_reg1
3
2.
clk_reg0 = j_tclk & j_update_gp_reg & j_gp_regsel[0]
3.
clk_reg1 = j_tclk & j_update_gp_reg & j_gp_regsel[1]
SI
SO
j_serial_data
j_tdi
clk_shfter
1
1.
clk_shfter = j_tclk & (j_shift_dr | j_capture_dr)
CLK
GEN
j_tclk
j_gp_regsel[1:0]
j_shift_dr
j_update_gp_reg
SHIFT
LOAD
j_capture_dr
j_shift_dr
j_capture_dr
j_trst_b
NOTES:
Содержание e200z3
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