33793 Datasheet, PDF (12/27 Pages) Freescale Semiconductor, Inc – Distributed System Interface (DSI) Sensor Interface

FUNCTIONAL DESCRIPTION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
• Read the general purpose I/O logic values and respond
to request for these values.
• Generating a cycle redundancy check (CRC) for the
received data and transmitted data in conformance with
the DSI Bus Standard.
Additionally, the control logic performs error checking on
the received data. If errors are found, no action is taken and
no response is made. Errors include:
• CRC received doesn’t match CRC of received data.
• Number of received bits is not 12 or 20.
CLOCK
The clock is a low-stability type with the capacitor
integrated onto the die. The signaling system and all internal
operations are such that no external precision timing device
is needed in the normal operation of this device.
BUS SWITCH (BUSSW)
The bus switch passes signaling and power to all
subsequent devices on the bus. It can block a voltage of
either polarity up to the highest idle state level between
BUSIN and BUSOUT.
LOGICOUT
LOGICOUT is a logic level output with enhanced high-side
drive capability.
ADDRESSING
The 33793 IC supports both runtime programmable and
pre-programmed addressing as defined in the DSI
Specification. Runtime programmable addressing uses the
daisy chain bus connection. Pre-programmed devices may
either be connected in daisy chain or in parallel on the bus
wires.
Programmable address devices all power up with a device
address of $0 in their address register and their bus switches
open. In the daisy chain, if the first device receives the
initialization command device on BUSIN, it will accept the
address in the command and close its switch at the end of the
command. The next device in the chain will now be able to
receive the initialization command on its BUSIN and will
accept the next address. This proceeds down the chain until
the last device is addressed. The devices can also be
initialized by the reverse initialization command if the signal is
applied to BUSOUT.
Pre-programmed devices power up with their pre-
programmed address in its address register. It will ignore all
Initialization commands unless the address in the command
matches its pre-programmed address. In this event the
device stores the other information contained in the
Initialization command.
33793
12
Analog Integrated Circuit Device Data
Freescale Semiconductor