I think you are referring to SW1 (the DIPS_08 model). This switch is
normally not installed for a single MOBO. The
purpose is to allow additional I2C addressing for multiple boards. Each
connection is pulled up with resistor, so that the
default is a logic "1". If a switch is installed and the position is
turned "ON": then the switch shorts this connection to ground, making
a logic "0".
Look at the schematic for the Switch position and the corresponding I2C
device addressing pins.
Here is a summary of the default I2C addressing and possible switch
selected addresses:
I2C Addresses (7bit hex addressing shown)
Mobo v4.3 (x = DIP switch selectable, r = 1 for read, 0 for write)
Device Default Def Jumper/SW Can be Binary
Si570 0x55 0x55 1010101r
AD5301 DAC 0x0d 1 0x0c, 0x0d 000110xr
AD7991-0 ADC 0x28 0x28 0101000r
AD7991-1 ADC 0x29 0x29 0101001r
TMP100 Temp Sensor 0x4e 11 0x48, 0x4a, 0x4c, 0x4e
1001xx0r
PCF8574A 0x3f 111 0x38. 0x39, 0x3a, 0x3b, 0111xxxr
0x3c, 0x3d, 0x3e, 0x3f
DS1086 0x58 000 0x58, 0x59, 0x5a, 0x5b 1011xxxr
0x5c, 0x5d, 0x5e, 0x5f
Mike Collins KM2J (was KF4BQ)