LPC47S457-NC SMSC [SMSC Corporation], LPC47S457-NC Datasheet - Page 258

• Manufacturer Part Number: LPC47S457-NC
• Description: Advanced I/O with X-Bus Interface
• Manufacturer: SMSC [SMSC Corporation]

Introduction
The LPC47S45x provides board test capability through the XNOR chain. When the chip is in the XNOR chain test
mode, setting the state of any of the input pins to the opposite of its current state will cause the output of the chain to
toggle.
All pins on the chip are inputs to the XNOR chain, with the exception of the following:
To put the chip in the XNOR chain test mode, tie LAD0 (pin 23) and LFRAME# (pin 27) low.
PCI_RESET# (pin 29) from a low to a high state. Once the chip is put into XNOR chain test mode, LAD0 (pin 23) and
LFRAME# (pin 27) become part of the chain.
To exit the XNOR chain test mode tie LAD0 (pin 23) or LFRAME# (pin 27) high. Then toggle PCI_RESET# (pin 29)
from a low to a high state. A VCC POR will also cause the XNOR chain test mode to be exited. To verify the test
mode has been exited, observe the output onTXD1 (PIN 88). Toggling any of the input pins should not cause its state
to change.
Setup
Warning: Ensure power supply is off during setup.
Testing
SMSC LPC47S45x
1.
2.
3.
4.
5.
6.
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
I/O#1
VCC (pins 21, 68, & 96), VTR (pins 1, 56, & 125), and Vbat (pin 2).
VSS (pins 34, 63, 79, & 106) and AVSS (pin 5)
TXD1 (PIN 88). This is the chain output.
PCI_RESET# (pin 29
XTAL1 and XTAL2 (pins 3 and 4).
XOSEL (pin 124)
Connect VSS (pins 34, 63, 79, & 106) to ground.
Connect AVSS (pin 5) to analog ground.
Connect VCC (pins 21, 68, & 96), VTR (pins 1, 56, & 125), & Vbat (pin 2) to VCC (3.3V).
Connect an oscilloscope or voltmeter to output pin TXD1 (PIN 88).
All other pins should be tied to ground, except XTAL1 (pin 3), XTAL2 (pin 4), and XOSEL (pin 124).
Turn power on.
With LAD0 (pin 23) and nLFRAME (pins 27) low, bring PCI_RESET# (pin 29) high. The chip is now in
XNOR chain test mode. At this point, all inputs to the XNOR chain are low. The output on TXD1 (PIN 88)
should also be low. Refer to INITIAL CONFIG on Truth Table 1.
Bring pin 128 high. The output on TXD1 (PIN 88) should go high. Refer to STEP ONE on Truth Table 1.
In descending pin order, bring each input of the XNOR chain high. The output should switch states each
time an input is toggled. Continue until all inputs are high. The output on TXD1 (PIN 88) should now be
high. Refer to END CONFIG on Truth Table 1.
The current state of the chip is now represented by INITIAL CONFIG in Truth Table 2.
I/O#2
FIGURE 50 – XNOR-CHAIN TEST STRUCTURE
DATASHEET
I/O#3
Page 258 of 259
I/O#n
Then toggle
XNor
Out
Rev. 06-01-06