33975 Datasheet, PDF (17/32 Pages) Freescale Semiconductor, Inc – Multiple Switch Detection Interface with Suppressed Wake-Up and 32mA Wetting Current

FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
ANALOG SELECT REGISTER
bit 6 and bit 5 to 1,1 in the Analog Select Register is not
The analog voltage on switch inputs may be read by the
MCU using the analog command (refer to Table 11). Internal
allowed and will place the input as an analog input with high
impedance.
to the IC is a 22-to-1 analog multiplexer. The voltage present
Analog currents set by the analog command are pull-up
on the selected input terminal is buffered and made available
currents for all SGn and SPn inputs (refer to Table 11). The
on the AMUX output terminal. The AMUX output terminal is
analog command does not allow pull-down currents on the
clamped to a maximum of VDD volts regardless of the higher
SPn inputs. Setting the current to 32 mA or 4.0 mA may be
voltages present on the input terminal. After an input has
useful for reading sensor inputs. Further information is
been selected as the analog, the corresponding bit in the next
provided in the Typical Applications section of this datasheet
SO data stream will be logic [0]. When selecting a channel to
beginning on page 22. The MCU may change or update the
be read as analog, the user must also set the desired current
Analog Select Register via software at any time in Normal
(32 mA, 4.0 mA, or high impedance). Setting bit 6 and bit 5 to
mode.
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
Table 11. Analog Command
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
Table 12. Analog Channel
Bits 43210
Analog Channel Select
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
10000
10001
10010
10011
10100
10101
10110
No Input Selected
SG0
SG1
SG2
SG3
SG4
SG5
SG6
SG7
SG8
SG9
SG10
SG11
SG12
SG13
SP0
SP1
SP2
SP3
SP4
SP5
SP6
SP7
Analog Integrated Circuit Device Data
Freescale Semiconductor
33975
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