CY3220LINBUS-RD Cypress Semiconductor Corp, CY3220LINBUS-RD Datasheet - Page 14

• Manufacturer Part Number: CY3220LINBUS-RD
• Description: KIT REF DESIGN LIN BUS
• Manufacturer: Cypress Semiconductor Corp
• Series: PSoC®r

Specifications of CY3220LINBUS-RD

• Main Purpose: Interface, LIN
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: CY8C27143, CY8C27443
• Processor To Be Evaluated: CY8C27143-24PXI and CY8C27443-24PXI
• Interface Type: RS-232
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant
• Other names: 428-1926

2. System Architecture
Figure 2-2. Structure of a Byte Field
2.3.2
The break symbol is used to signal the beginning of a new
frame. It is the only field that does not comply with Figure 2-
2. A break is always generated by the master and is at least
13 bits of dominant value, including the start bit, followed by
a break delimiter, as shown in Figure 2-3. The break delim-
iter is at least one nominal bit-time long. A slave node uses
a break detection threshold of 11 nominal bit times.
Figure 2-3. The Break Field
2.3.3
The synch byte is sent to the slave to synchronize to the
master’s baud rate. The synch byte is nothing but a data
field with 0x55 as data. The synch byte is shown in Figure 3-
4.
Figure 2-4. The Synch Byte
The slave measures the time between the start bit and the
fourth falling edge of the synch byte. Then dividing this by
eight, gives the single bit time. Based upon this time, the
slave sets the clock to its UART so that it can send/receive
the data bytes of the frame at the master’s bit rate.
2.3.4
The byte that follows the synch byte is the protected identi-
fier. This byte has two parts. Bits 0-5 form the actual identi-
fier (0 to 63). Bits 6 and 7 form the identifier parity. The
identifiers can be split into four different categories:
■
12
Identifiers 0 - 59 are used for signal-carrying frames.
Break Field
Synch Byte
Protected Identifier
Cypress Semiconductor – Rev. **
■
■
■
More details on protected identifiers are in the LIN Bus 2.0
specifications at http://www.linsubbus.org.
2.3.5
The protected Identifier is followed by 1 to 8 bytes of data.
The number of data bytes carried by a frame is defined in
the LIN definition file (LDF). This file also defines whether
the data bytes are sent from the master to a slave or from a
slave to the master. Data that are longer than 1 byte are
transmitted LSB first (Little Endian mode).
2.3.6
The last field of a frame is the checksum. The checksum
contains the inverted 8-bit sum with carry over all data bytes
or all data bytes and the protected identifier. Checksum cal-
culation over only the data bytes is called classic checksum
and is used for communication with LIN bus 1.x slaves.
Checksum calculation over both the data bytes and the pro-
tected identifier byte is called enhanced checksum and it is
used for communication with LIN bus 2.0 slaves. The check-
sum is transmitted in a byte field. Use of classic or
enhanced checksum is managed by the master node and
determined per frame identifier; classic in communication
with LIN bus 1.x slave nodes and enhanced in communica-
tion with LIN bus 2.0 slave nodes. Identifiers 60 (0x3c) to 63
(0x3f) always use classic checksum.
The complete LIN standard is available at
bus.org.
2.3.7
Only the master initiates a frame. The master allocates a
time slot for each frame. The master also sends the frames
in a predetermined sequence. The information sequence of
the frames and the time slot for each frame is available in a
table called Schedule table. Each entry of this table
describes the protected identifier of the frame to be initiated
and also the time to be allotted for that frame. When all the
Identifiers 60 (0x3C) and 61 (0x3D) are used for diag-
nostic frames.
Identifier 62 (0x3E) is used for user-defined extensions.
Identifier 63 (0x3F) is used for future protocol enhance-
ments.
Data
Checksum
Frame Transfers on the LIN Bus
LIN Bus 2.0 Reference Design
October 25, 2006
http://www.linsub-