CR16MCS9VJE8 National Semiconductor, CR16MCS9VJE8 Datasheet - Page 88

• Manufacturer Part Number: CR16MCS9VJE8
• Description: 16-Bit Microcontroller IC
• Manufacturer: National Semiconductor

Specifications of CR16MCS9VJE8

• Controller Family/series: CR16X
• Core Size: 16 Bit
• Program Memory Size: 64K X 8 Flash
• Digital Ic Case Style: PQFP
• No. Of Pins: 80
• Mounting Type: Surface Mount
• Clock Frequency: 25MHz
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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Frame Fields
Data and remote frames consist of the following different bit
fields:
The Start of Frame indicates the beginning of data and re-
mote frames. It consists of a single 'dominant' bit. A node is
only allowed to start transmission when the bus is idle. All
nodes have to synchronize to the leading edge (first edge af-
ter the bus was idle) caused by SOF of the node which starts
transmission first.
The Arbitration field consists of the identifier field and the
RTR (Remote Transmission Request) bit. For extended
frames there is also a SRR (Substitute Remote Request) and
a IDE (ID Extension) bit inserted between ID18 and ID17 of
the identifier field. The value of the RTR bit is 'dominant' in a
data frame and 'recessive' in a remote frame.
The Control field consists of six bits. For standard frames it
starts with the ID Extension bit (IDE) and a reserved bit
(RB0). For extended frames the control field starts with two
reserved bits (RB1, RB0). These bits are followed by the 4-
bit Data Length Code (DLC).
The CR16CAN receiver accepts all possible combinations of
the reserved bits (RB1, RB0). The transmitter must be con-
figured to send only '0' bits.
The DLC indicates the number of bytes in the data field. It
consists of four bits. The data field can be of length zero. The
admissible number of data bytes for a data frame ranges
from 0 to 8.
The Data field consists of the data to be transferred within a
data frame. It can contain 0 to 8 bytes. A remote frame has
no data field.
The CRC field consists of the CRC sequence followed by the
CRC delimiter. The CRC sequence is derived by the trans-
mitter from the modulo 2 division of the preceding bit fields,
starting with the SOF up to the end of the data field, excluding
stuff-bits, by the generator polynomial:
The remainder of this division is the CRC sequence transmit-
ted over the bus. On the receiver side, the module divides all
bit fields up to the CRC delimiter excluding stuff-bits, and
checks if the result is zero. This will then be interpreted as a
valid CRC. After the CRC sequence a single ‘recessive’ bit is
transmitted as the CRC delimiter.
original or destuffed bit
— Start of Frame
— Arbitration Field
— Control Field
— Data Field
— CRC Field
— ACK Field
— EOF Field
a. x = {0,1}
stuffed bit stream
x
stream
1 5
+ x
14
+ x
10
+ x
1000001111101x
10000011111x
8
+ x
7
+ x
4
+ x
a
3
+ 1
0111110000010x
01111100000x
88
The ACK field is two bits long and contains the ACK slot and
the ACK delimiter. The ACK slot is filled with a ‘recessive’ bit
by the transmitter. This bit is overwritten with a ‘dominant’ bit
by every receiver that has received a correct CRC sequence.
The second bit of the ACK field is a ‘recessive’ bit called the
acknowledge delimiter.
The End of Frame field closes a data and a remote frame.
It consists of seven ‘recessive’ bits.
Data Frame
The structure of a standard and extended data frame is
shown in Figure46.
A CAN data frame consists of the following fields as previ-
ously described:
Remote Frame
Figure47 shows the structure of a standard and extended re-
mote frame.
A remote frame is comprised of the following fields sections,
which is the same as a data frame (see Frame Fields on
page 88) except for the data field, which is not present.
Note that the DLC must have the same value as the corre-
sponding data frame to prevent contention on the bus. The
RTR bit is ‘recessive’.
— Start of Frame (SOF)
— Arbitration field + Extended Arbitration
— Control field
— Data field
— Cyclic Redundancy Check field (CRC)
— Acknowledgment field (ACK)
— End of Frame (EOF)
— Start of Frame (SOF)
— Arbitration field + Extended Arbitration
— Control field
— Cyclic Redundancy Check field (CRC)
— Acknowledgment field (ACK)
— End of Frame (EOF)