ZAMC4100 Datasheet, PDF (117/155 Pages) Integrated Device Technology – Actuator and Motor Controller

ZAMC4100 Datasheet
4.9. SW-LIN Module
The SW-LIN provides the logic for communication on the LIN bus via the LIN PHY within the SBC. It is compliant
with LIN Specifications Rev. 2.1 and operates as a LIN SLAVE only. Most of the protocol must be handled in
software.
Figure 4.6 SW-LIN Block Diagram
BreakSync
Detector
CTRL SIGNAL
SYNC;BANDRATE
Inactivity
Timer
TIMEOUT
CTRL SIGNAL
Data Unit
(LIN UART)
LIN RXD
LIN
SBC
RX Sync & Filter
LIN-PHY
LIN TXD
IRQ
SBC
MCU
The hardware consists of a BREAK/SYNC field detector for bus synchronization and baud rate detection, an
inactivity timer, a data unit similar to a UART for communication, and a small block to synchronize and filter the
incoming data line.
The BREAK/SYNC field detector is used to detect any occurrence of a BREAK field and a SYNC field as
described in the LIN standard on the bus. It generates a sync strobe at the rising edge of RXD at the beginning of
the STOP bit and updates the baud rate as needed. The LIN standard defines the baud rate as being between
1kBaud and 20kBaud; however the SW-LIN is able to operate at even higher baud rates. The maximum baud rate
depends on the clock divider value and whether or not the LIN is operating in fast mode. In slow mode, the
maximum baud rate is 30kBaud independent of the clock divider value. In fast mode, the maximum baud rate is
75kBaud for a clock divider value of 3, 150kBaud for a clock divider value of 2, and 200kBaud for others.
The inactivity timer observes the RXD line and generates an interrupt when the LIN bus is inactive for more than 4
seconds as required by the LIN standard.
4.9.1. The Inactivity Timer
The SW-LIN contains an inactivity timer. This module is required as the LIN standard requires that a LIN SLAVE
goes to sleep after more than 4s but less than 10s of inactivity on the bus. As bus inactivity means that there is no
change on the bus regardless of whether the bus is high or low, a timer is implemented which is reset on each
transition on the bus (falling or rising edge of the RXD line) and which is incremented when the timer has not
expired. When this timer expires, an interrupt is generated so that the software can disable the SW-LIN.
The LIN standard describes two ways of going to sleep. In addition to the inactivity timeout, the LIN SLAVES must
go to sleep when the corresponding SLEEP command has been received. If the LIN master in the full application
guarantees that a SLEEP command is always sent if the bus is not required anymore and a timeout can never
occur. The software can disable the inactivity timer to save power.
© 2016 Integrated Device Technology, Inc.
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January 26, 2016