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MC33975R2

Multiple Switch Detection Interface with Suppressed Wake-up and 32 mA Wetting Current

Freescale Semiconductor 

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

Table 9. Wetting Current Timer Enable Command

Wetting Current Timer Commands

Command Bits

23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

0 0 0 0 0 1 1 1 X X X X X X X X sp7 sp6 sp5 sp4 sp3 sp2 sp1 sp0

0 0 0 0 1 0 0 0 X X sg1 sg1 sg1 sg1 sg9 sg8 sg7 sg6 sg5 sg4 sg3 sg2 sg1 sg0

3210

TRI-STATE REGISTER

The tri-state command is use to set the SPn or SGn input

node as high-impedance (refer to Table 10). By setting the

Tri-state Register bit to logic [1], the input will be high-

impedance regardless of the metallic command setting. The

comparator on each input remains active. This command

allows the use of each input as a comparator with a 4.0 V

threshold. The MCU may change or update the Tri-state

Register via software at any time in Normal mode.

Table 10. Tri-state Command

Tri-State Commands

Command Bits

23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

0 0 0 0 1 0 0 1XX X

X

X

X X X sp7 sp6 sp5 sp4 sp3 sp2 sp1 sp0

0 0 0 0 1 0 1 0 X X sg13 sg12 sg11 sg10 sg9 sg8 sg7 sg6 sg5 sg4 sg3 sg2 sg1 sg0

ANALOG SELECT REGISTER

The analog voltage on switch inputs may be read by the MCU

using the analog command (refer to Table 11). Internal to the

IC is a 22-to-1 analog multiplexer. The voltage present on the

selected input pin is buffered and made available on the

AMUX output pin. The AMUX output pin is clamped to a

maximum of VDD volts regardless of the higher voltages

present on the input pin. After an input has been selected as

the analog, the corresponding bit in the next SO data stream

will be logic [0]. When selecting a channel to be read as

analog, the user must also set the desired current (32 mA,

4.0 mA, or high-impedance). Setting bit 6 and bit 5 to 0,0

selects the input as high-impedance. Setting bit 6 and bit 5 to

0,1 selects 4.0 mA, and 1,0 selects 32 mA. Setting bit 6 and

bit 5 to 1,1 in the Analog Select Register is not allowed and

will place the input as an analog input with high-impedance.

Analog currents set by the analog command are pull-up

currents for all SGn and SPn inputs (refer to Table 11). The

analog command does not allow pull-down currents on the

SPn inputs. Setting the current to 32 or 4.0 mA may be useful

for reading sensor inputs. Further information is provided in

the Typical Applications section of this datasheet beginning

on page 23. The MCU may change or update the Analog

Select Register via software at any time in Normal mode.

Analog Command

Table 11. Analog Command

Not used

Current

Select

Analog Channel Select

23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

0 0 0 0 0 1 1 0 X X X X X X X X X 32 4.0 0 0 0 0 0

mA mA

33975

18

Analog Integrated Circuit Device Data

Freescale Semiconductor

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