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Logic
State
Description
Comments
0
PGA309 operates in “Normal / Stand-
Alone Mode”.
Reads external EEPROM and uses
temperature coefficients to update Gain DAC
and Zero DAC settings.
P7
Test pin
1
PGA309 operates in “Test Mode”.
No external EEPROM reads and must be
manually written to for changes in DACs or
register settings.
0
Turns on LED D2 on PGA309 PC
Interface Board.
LED D2 is turned on by the Board Control
Software if “PGA309 Test Pin HIGH” box in
the Main Window is checked.
P6
nLED2
1
Turns off LED D2 on PGA309 PC
Interface Board.
LED D2 is turned off by the Board Control
Software if “PGA309 Test Pin HIGH” box in
the Main Window is not checked.
0
Turns on LED D1 on PGA309 PC
Interface Board.
LED D1 is turned on by the Board Control
Software when successful communication has
been completed after power-on from zero
volts on the PC Interface Board.
P5
nLED1
1
Turns off LED D1 on PGA309 PC
Interface Board.
0
Normal ADS1100 input operation.
P4
ADS1100
Cal
1
Shorts ADS1100 inputs (V
IN+
and V
IN-
)
together for offset calibration.
Used in the ADS1100 calibration sequence by
the Board Control Program
0
P3
1
Logic output of port expander port P3,
PGA309 PC Interface Board, U5,
pin 7.
Spare port expander port available for user
application if desired.
0
Disables the Two-Wire interface from
the PGA309 Sensor Interface Board.
To allow reliable, uninterrupted connection to
ADS1100 and PCF8574A when PGA309 is in
Stand-Alone Mode set this bit to zero.
P2
2Wen
1
Enables the Two-Wire interface from
the PGA309 Sensor Interface Board.
To allow for Two-Wire digital communication
from PC to PGA309 and external EEPROM.
0
Applies Vs to PGA309 Sensor
Interface Board.
Important when PRG is connected to Vout on
PGA309 to ensure One-Wire communication
during power-up.
P1
nVSen
1
Removes Vs from PGA309 Sensor
Interface Board.
Important when PRG is connected to Vout on
PGA309 to ensure One-Wire communication
during power-up.
0
Disable 4.7k
Ω
One-Wire pull-up
resistor.
Important to disable for unloaded PGA309
Vout accurate reading through ADS1100.
P0
1Wen
1
Enable 4.7k
Ω
One-Wire pull-up
resistor.
Table 6:
Functionality of
Port Expander (PCF8574A) Bits
(default initial values selected by the Board Control Software are highlighted in bold)
