MC33884 Datasheet, PDF (9/20 Pages) Motorola, Inc – Switch Monitor Interface

MC33884
CIRCUIT DESCRIPTION
Introduction
The MC33884 is a monolithic integrated circuit designed to
interface between external electrical system switches and low
voltage microprocessors via a Serial Peripheral Interface
(SPI). The MC33884 monitors the OPEN/CLOSED status of
multiple external switches used in a system. The MC33884
features 4 programmable Switch–to–Ground or Battery sense
inputs, 6 Switch–to–Ground sense inputs, 2
Switch–to–Battery sense inputs, programmable Wake–up
Timer, programmable Interrupt Timer, and programmable
wetting current settings. All inputs are protected for ESD
transients when implemented with the appropriate ESD
capacitor.
There are numerous applications for this device in aircraft,
aerospace, robotic, process & control, automotive, and
security systems. Potential applications exist where switch
status verification for safety, fault tolerant operation, or
process control function purposes are critical.
The MC33884 has four modes of operation: Sleep, Normal,
Polling, and Polling + INT Timer.
The MC33884 is designed to provide a robust interface
between system switch contacts and a microprocessor. Each
MC33884 input provides the switch contact with high levels of
wetting current during switch closure. After the input switch
has been closed for 20 ms, the wetting current is reduced,
hence reducing power dissipation in the IC. The response to
a SPI command will always return Switch Status,
Master/Slave, INT Flag, and Mode settings. The following
section describes the programming modes and features of the
MC33884.
Two or more MC33884 devices may be used in a module
system when implemented in a parallel or serial configuration.
Figure 5 and Figure 6 show the parallel and serial
configurations respectively. When using the Serial
configuration, 32 clock cycles are required for a complete
transfer of data to the MC33884.
MC68HCXX
Microcontroller
MOSI
16 Bit Shift Register
MISO
SI
MC33884
SO
SCLK
Parallel
Ports
INT
SCLK
CS
RSTB
INTB
SI
MC33884
SO
SCLK
CS
RSTB
INTB
Microprocessor Interface
The MC33884 directly interfaces to 3.3 or 5.0 V MCU. SPI
serial clock frequencies in excess of 5.0 MHz may be used for
programming and reading switch input status. Figure 4 shows
the configuration between an MCU and one MC33884.
MC68HCXX
Microcontroller
MOSI
16 Bit Shift Register
MISO
MC33884
SI
16 Bit Shift Register
SO
Receive
Buffer
Parallel
Ports
SCLK
RSTB
CS
INT
INTB
To
Logic
Figure 4. SPI Interface with Microprocessor
Figure 5. SPI Parallel Interface with Microprocessor
MC68HCXX
Microcontroller
MOSI
16 Bit Shift Register
MISO
SI
MC33884
SO
SCLK
Parallel
Ports
INT
SCLK
CS
RSTB
INTB
SI
MC33884
SO
SCLK
The MC33884, though originally designed for automotive
use, is very useful in a variety of other applications, i.e.,
computer, telecommunications, and industrial fields. It is
parametrically specified over an input battery/supply voltage
of 9.0 to 16.0 V but is designed to operate over a considerably
wider range of 5.5 to 26.5 V.
CS
RSTB
INTB
Figure 6. SPI Serial Interface with Microprocessor
MOTOROLA TSG IC DEVICE DATA
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