
2000 Jul 26
59
Philips Semiconductors
Preliminary Specification
Single-chip 8-bit microcontroller with CAN controller
P8xC591
12.5.19.1 Descriptor File of the Receive Buffer
Identifier,FrameFormat,RemoteTransmissionRequestbitandDataLengthCodehavethesamemeaningasdescribed
in the Transmit Buffer.
Fig.22 Bit Layout Receive Buffer.
7
ID.28
6
ID.27
5
ID.26
4
ID.25
3
ID.24
2
ID.23
1
ID.22
0
ID.21
7
ID.28
6
ID.27
5
ID.26
4
ID.25
3
ID.24
2
ID.23
1
ID.22
0
ID.21
Addr. 97
RX Identifier 1
Addr. 97
RX Identifier 1
Standard Frame Format (SFF)
Extended Frame Format (EFF)
7
ID.20
6
ID.19
5
ID.18
4
RTR
3
0
2
0
1
0
0
0
Addr. 98
RX Identifier 2
7
ID.20
6
ID.19
5
ID.18
4
ID.17
3
ID.16
2
ID.15
1
ID.14
0
ID.13
Addr. 98
RX Identifier 2
7
ID.12
6
ID.11
5
ID.10
4
ID.9
3
ID.8
2
ID.7
1
ID.6
0
ID.5
Addr. 99
RX Identifier 3
7
ID.4
6
ID.3
5
ID.2
4
ID.1
3
ID.0
2
RTR
1
0
0
0
Addr. 100
RX Identifier 4
Meaning of the Receive Buffer Bits:
ID.x
FF
RTR
DLC.x
Identifier bit x
Frame Format
Remote Transmission Request
Data Length Code bit x
7
FF
6
RTR
5
0
4
0
3
DLC.3
2
DLC.2
1
DLC.1
0
DLC.0
Addr. 96
RX Frame Information
7
FF
6
RTR
5
0
4
0
3
DLC.3
2
DLC.2
1
DLC.1
0
DLC.0
Addr. 96
RX Frame Information
Note:
The received Data Length Code located in the Frame
Information Byte represents the real sent Data Length
Code, which may be greater than 8 (depends on
transmitting CAN node). Nevertheless, the maximum
number of received data bytes is 8. This should be taken
into account by reading a message from the Receive
Buffer.
It depends on the data length how many CAN messages
can fit in the RXFIFO at one time. If there is not enough
space for a new message within the RXFIFO, the CAN
controller generates a Data Overrun condition the moment
this message becomes valid and the acceptance test was
positive. A message that is partly written into the RXFIFO,
when the Data Overrun situation occurs, is deleted. This
situation is signalled to the CPU via the Status Register
and the Data Overrun Interrupt, if enabled.