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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262-004US
129
Intel XScale
®
Processor—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
A Capture_DR loads TXRXCTRL[31] into DBG_SR[0]. The other bits in DBG_SR are
loaded as shown in
.
The captured data is scanned out during the Shift_DR state.
Care must be taken while scanning in data. While polling TXRXCTRL[31], incorrectly
setting DBG_SR[35] or DBG_SR[1] may cause unpredictable behavior following an
Update_DR.
Update_DR parallel loads DBG_SR[35:1] into DBG_REG[34:0]. Whether the new data
gets written to the RX register or an overflow condition is detected depends on the
inputs to the RX write logic.
3.6.11.6.1
Rx Write Logic
) serves 4 functions:
• Enable the debugger write to RX - the logic ensures only new, valid data from the
debugger is written to RX. In particular, when the debugger polls TXRXCTRL[31] to
see whether the debug handler has read the previous data from RX. The JTAG state
machine must go through Update_DR, which should not modify RX.
• Clear DBG_REG[34] - mainly to support high-speed download. During high-speed
download, the debugger continuously scan in a data to send to the debug handler
Figure 16.
DBGRX Hardware
B4342-01
1
2
33
34
TDO
TDI
DBG_SR
Capture_DR
Update_DR
DBG_REG
1
2
3
34
35
delay
0
31
software read
TXRXCTRL
RX
TCK
Core CLK
software read/write
0
0
0
0
1
30
31
29
RX
DBG_REG[1]
Write
Logic
Flush RR
to TXRXCTRL[29]
TXRXCTRL[31]
set TXRXCTRL[31]
clear by SW read from RX
set by Debugger Write
clear DBG_REG[34]
undefined
enable
set overflow