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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262-004US
125
Intel XScale
®
Processor—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
3.6.11.1
SELDCSR JTAG Command
The ‘SELDCSR’ JTAG instruction selects the DCSR JTAG data register. The JTAG op code
is ‘01001’. When the SELDCSR JTAG instruction is in the JTAG instruction register, the
debugger can directly access the Debug Control and Status Register (DCSR). The
debugger can only modify certain bits through JTAG, but can read the entire register.
The SELDCSR instruction also allows the debugger to generate an external debug
break.
3.6.11.2
SELDCSR JTAG Register
Placing the “SELDCSR” JTAG instruction in the JTAG IR, selects the DCSR JTAG Data
register (
), allowing the debugger to access the DCSR, generate an external
debug break, set the hold_rst signal, which is used when loading code into the
instruction cache during reset.
A Capture_DR loads the current DCSR value into DBG_SR[34:3]. The other bits in
DBG_SR are loaded as shown in
A new DCSR value can be scanned into DBG_SR, and the previous value out, during the
Shift_DR state. When scanning in a new DCSR value into the DBG_SR, care must be
taken to also set up DBG_SR[2:1] to prevent undesirable behavior.
Figure 13.
SELDCSR Hardware
B4338-01
TDO
TDI
DBG_SR
Capture_DR
Update_DR
DBG_REG
1
2
3
34
35
0
31
software read/write
DCSR
TCK
Core CLK
0
0
0
1 0
1
2
33
34
0
ignored
hold_rst
external debug break