MC33972A FREESCALE [Freescale Semiconductor, Inc], MC33972A Datasheet - Page 19

• Manufacturer Part Number: MC33972A
• Description: Multiple Switch Detection Interface with Suppressed Wake-Up
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Table 17. Serial Output (SO) Response Register
EXAMPLE OF NORMAL MODE OPERATION
the states of the programmable internal control registers. A
typical application may have the following settings:
generated with each switch contact change of state (open-to-
close or close-to-open) and 16mA of contact wetting current
will be source for 20ms. The
switch status is acknowledged by the microprocessor. It is
critical to understand
edge of
maximum duration a switch state change can exist without
acknowledgement depends on the software response time to
the interrupt.
between changing input states and the
interrupt command) from the 33972 device and read the
switch states on a periodic basis. Switch activation and
deactivation faster than the MCU read rate will not be
acknowledged.
Sleep Mode only with a valid sleep command.
Table 18. Sleep Command
SO Response Will
Always Send
Analog Integrated Circuit Device Data
Freescale Semiconductor
23
0
The operation of the device in Normal Mode is defined by
• Programmable switch – set to switch-to-ground
• All inputs set as wake-up
• Wetting current on (16mA)
• Wetting current timer on (20ms)
• All inputs tri-state-disabled (comparator is active)
• Analog select 00000 (no input channel selected)
With the device programmed as above, an interrupt will be
If desired the user may disable interrupts (wake up/
The 33972 device will exit the Normal Mode and enter the
22
0
CS
if a switch closure occurs while
21
0
Figure
Sleep Command
them
flg
20
0
6, page 9, shows the interaction
int
flg
INT
19
1
SP7
will not be cleared on the rising
Table 16. Serial Output (SO) Bit Data
18
1
INT
SP6
Type of Input
pin will remain LOW until
17
0
SP5
SG
SP
16
SP4
0
INT
CS
SP3
and
15
X
Switch to Ground
Switch to Ground
Switch to Battery
Switch to Battery
is LOW. The
CS
Programmed
SP2
14
X
pins.
Input
N/A
N/A
SP1
13
X
SP0 SG13 SG12 SG11 SG10 SG9
12
X
11
X
SLEEP MODE
Sleep Mode may be entered only by sending the sleep
command. All register settings programmed in Normal Mode
will be maintained in Sleep Mode.
when any of the following events occur:
Sleep Mode. However removing V
Mode will disable a wake-up from falling edge of
first SO data message is not valid.
programmable timers for Sleep Mode, the interrupt timer and
the scan timer, as shown in
used as a periodic wake-up timer. When the timer expires, an
interrupt is generated and the device enters Normal Mode.
disabled by programming the interrupt bits to logic [1 1 1].
timer.
SGn < 4.0V
SGn > 4.0V
Voltage on
SPn < 4.0V
SPn > 4.0V
SPn < 4.0V
SPn > 4.0V
Input Pin
Sleep Mode is used to reduce system quiescent currents.
The 33972 will exit Sleep Mode and enter Normal Mode
• Input switch change of state (when enabled)
• Interrupt timer expire
• Falling edge of
• Falling edge of
• Falling edge of
• Power-ON Reset (POR)
The V
Note In cases where
The sleep command contains settings for two
Note The interrupt timer in the 33972 device may be
Table 19
10
X
Logic [1])
DD
X
9
Command Bits
supply may be removed from the device during
shows the programmable settings of the Interrupt
X
8
SG8
SO SPI Bit
X
7
WAKE
INT
CS
SG7
1
0
0
1
1
0
(with V
(with V
CS
6
X
FUNCTIONAL DEVICE OPERATION
Table 18
SG6
is used to wake the device, the
5
DD
DD
SG5
DD
= 5.0V)
= 5.0V and
4
from the device in Sleep
OPERATIONAL MODES
The interrupt timer is
SG4
3
SG3
WAKE
2
SG2
INT
SG1
1
and
at
33972
SG0
CS
0
19
.