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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—Intel XScale
®
Processor
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
144
Order Number: 306262-004US
An external host should take the following steps to load code into the instruction cache
following a cold reset:
1. Assert the Reset and JTG_TRST_N pins: This resets the JTAG IR to IDCODE and
invalidates the instruction cache (main and mini).
2. Load the SELDCSR JTAG instruction into JTAG IR and scan in a value to set the Halt
Mode bit in DCSR and to set the hold_rst signal. For details of the SELDCSR, refer
“SELDCSR JTAG Register” on page 125
3. After hold_rst is set, de-assert the Reset pin. Internally the processor remains held
in reset.
4. After Reset is de-asserted, wait 2030 TCKs.
5. Load the LDIC JTAG instruction into JTAG IR.
6. Download code into instruction cache in 33-bit packets as described in
.
7. After code download is complete, clock a minimum of 15 TCKs following the last
update_dr in LDIC mode.
8. Place the SELDCSR JTAG instruction into the JTAG IR and scan in a value to clear
the hold_rst signal. The Halt Mode bit must remain set to prevent the instruction
cache from being invalidated.
9. When hold_rst is cleared, internal reset is de-asserted, and the processor executes
the reset vector at address 0.
Figure 24.
Code Download During a Cold Reset For Debug
B4351-01
Internal
TRST
JTAG IR
RESET invalidates IC
Enter LDIC mode
RESET does not affect IC
TRST resets JTAG IR to IDCODE
IDCODE
set hold_rst signal
clear hold_rst signal
Reset Pin
RESET
RESET pin asserted until hold_rst signal is set
Processor branches
hold_rst
hold_rst keeps internal reset asserted
SELDCSR
SELDCSR
keep Halt Mode bit set
clock 15 tcks after
Download code
set Halt Mode bit
to address 0
LDIC
wait 2030 tcks after
Reset deasserted
last update_dr
in LDIC mode