ADUC7034 Datasheet, PDF (127/142 Pages) Analog Devices – Integrated Precision Battery Sensor for Automotive

Preliminary Technical Data
LIN HARDWARE INTERFACE
LIN Frame Protocol
The LIN frame protocol is broken into four main categories:
break symbol, sync byte, protected identifier, and data bytes.
The format of the frame header, break, synchronization byte,
and protected identifier are shown in Figure 44. Essentially, the
embedded UART, LIN hardware synchronization logic, and the
high voltage transceiver interface all combine on-chip to
support and manage LIN-based transmissions and receptions.
LIN Frame Break Symbol
As shown in Figure 45, the LIN break symbol is used to signal
the start of a new frame. It lasts at least 13 bit periods and a slave
must be able to detect a break symbol, even if it expects data or is
in the process of receiving data. The ADuC7034 accomplishes this
by using the LHSVAL1 break condition and break error detect
functionality as described earlier. The break period does not
have to be accurately measured, but if a bus fault condition (bus
held low) occurs, it must be flagged.
LIN Frame Synchronization Byte
The baud rate of the communication using LIN is calculated
from the sync byte, as shown in Figure 46. The time between
the first falling edge of the sync field and the fifth falling edge of
the sync field is measured. This result is divided by eight to give
the baud rate of the data that is going to be transmitted. The
ADuC7034 implement the timing of this sync byte in hardware.
For more information on this feature, please refer to the LIN
Hardware Synchronization Status Register section.
LIN Frame Protected Identifier
After receiving the LIN sync field, the required baud rate for
the UART is calculated. The UART is then configured, allowing
the ADuC7034 to receive the protected identifier, as shown in
Figure 47. The protected identifier consists of two subfields: the
identifier and the identifier parity. The six-bit identifier
contains the identifier of the target for the frame. The identifier
signifies the number of data bytes to be either received or trans-
mitted. The number of bytes is user-configurable at the system
level design. The parity is calculated on the identifier, and is
dependent on the revision of LIN for which the system is
designed.
ADuC7034
LIN Frame Data Byte
The data byte frame carries between one and eight bytes of
data. The number of bytes contained in the frame is dependent
on the LIN master. The data byte frame is split into data bytes
as shown in Figure 48.
LIN Frame Data Transmission and Reception
When the break symbol and synchronization byte have been
correctly received, data is transmitted and received via the
COMTX and COMRX MMRs, after configuration of the UART
to the required baud rate. To configure the UART for use with
LIN requires the use of the following UART MMRs:
COMDIV0: divisor latch (low byte).
COMDIV1: divisor latch (high byte).
COMDIV2: 16-bit fractional baud divide register. The required
values for COMDIV0, COMDIV1, and COMDIV2 are derived
from the LHSVAL0, to generate the required baud rate.
COMCON0: line control register. As soon as the UART is
correctly configured, the LIN protocol for receiving and
transmitting data is identical to the UART specification.
To manage data on the LIN bus requires use of the following
UART MMRs:
COMTX: 8-bit transmit register.
COMRX: 8-bit receive register.
COMCON0: line control register.
COMSTA0: line status register.
To transmit data on the LIN bus requires that the relevant data
be placed into COMTX. To read data received on the LIN bus
requires the monitoring of COMRX. To ensure that data is
received or transmitted correctly, COMSTA0 is monitored. For
more information refer to the UART Serial Interface and UART
Register Definition sections of this data sheet.
Under software control, it is possible to multiplex the UART
data lines (TxD and RxD) to external GPIO pins (GPIO_7 and
GPIO_8). For more information, refer to the description of the
GPIO Port1 Control Register (GP1CON) section.
Rev. Pr.A | Page 127 of 142