1996 Jun 27
48
Philips Semiconductors
Product specication
8-bit microcontroller with on-chip CAN
P8xCE598
Table 57 Description of the other DSCR2 bits
BIT
SYMBOL
FUNCTION
4RTR
Remote Transmission Request. If the RTR bit is:
HIGH (remote), then the Remote Frame will be transmitted by the CAN-controller.
LOW (data), then the Data Frame will be transmitted by the CAN-controller.
3
DLC.3
Data Length Code (DLC). The number of bytes (Data Byte Count) in the Data Field of a
message is coded by the Data Length Code. At the start of a Remote Frame transmission
the Data Length Code is not considered due to the RTR bit being HIGH (remote). This
forces the number of transmitted/received data bytes to be a logic 0. Nevertheless, the
Data Length Code must be specied correctly to avoid bus errors, if two CAN-controllers
start a Remote Frame transmission simultaneously. The range of the Data Byte Count is
0 to 8 bytes and coded as follows:
For reasons of compatibility no Data Byte Counts other than 0,1,2,....,8 should be used.
2
DLC.2
1
DLC.1
0
DLC.0
Data Byte Count
8DLC.3
4DLC.2
2DLC.1
DLC.0
+++
=
13.5.13.2 Data Field
The number of transferred data bytes is determined by the
Data Length Code. The first bit transmitted is the most
significant bit of data byte 1 at address 12.
13.5.14 RECEIVE BUFFER LAYOUT
The layout of the Receive Buffer and the individual bytes
correspond to the definitions given for the Transmit Buffer
layout, except that the addresses start at 20 instead of 10
(see Fig.15).
13.5.15 HANDLING OF THE CPU-CAN INTERFACE
Via the four special registers CANADR, CANDAT,
CANCON and CANSTA the CPU has access to the
CAN-controller and also to the DMA-logic. Note that
CANCON and CANSTA have different meanings for a
Read and Write access.
Table 58 The SFRs between CPU and CAN
Reserved bits are read as HIGH. R = Read; W = Write; R/W = Read/Write.
ADDRESS
ACCESS
BIT
76543210
CANADR
DBH
R/W
DMA
Reserved AutoInc
CANA4
CANA3
CANA2
CANA1
CANA0
CANDAT
DAH
R/W
CAND7
CAND6
CAND5
CAND4
CAND3
CAND2
CAND1
CAND0
CANCON; Do not use a RMW instruction
D9H
R
Reserved Reserved Reserved WUI
OI
EI
TI
RI
W
RX0A
RX1A
WUM
SLP
COS
RRB
AT
TR
CANSTA; The bit addresses of CANSTA (7 to 0) are DFH to D8H; do not use a RMW instruction
DFH to D8H R
BS
ES
TS
RS
TCS
TBS
DO
RBS
W
RAMA7
RAMA6
RAMA5
RAMA4
RAMA3
RAMA2
RAMA1
RAMA0