70353C Datasheet, PDF (5/76 Pages) Microchip Technology – Section 21. Enhanced Controller Area Network

Section 21. Enhanced Controller Area Network (ECAN™)
The Acknowledgement (ACK) field is sent as a recessive bit (logic level ‘1’), and is overwritten
as a dominant bit by any receiver that has received the data correctly. The message is
acknowledged by the receiver regardless of the result of the acceptance filter comparison.
The last field is the EOF field, which consists of seven recessive bits that indicate the end of
message.
Figure 21-4: Format of the Standard Data Frame
21
Interframe Space
S
O
F
9/19/_A20_rb0_i6_tr-_a9_ti/_o2_n6/2006
Field
IDENTIFIER
R
T
11 Bits
R
9/19/20_C0_o6_n-_tr9_o/2_l 6/2006
Field
I
D RB0
E
DLC
4 Bits
9/19/20_D06_a-_ta9/26/2006
Field
9/19/200_CF6_iRe-_lC99_d//2169//220000_FA66_{iCe- lK9d}9/1/296/ _/20EF0n6rad-_m-o9_e/_f2_-6/2006_Interframe
Space
DATA
8 Bytes
CRC
16 Bits
ACK
2 Bits
EOF
7 Bits
IFS
3 Bits
SID10
SID1 SID0
11-bit Identifier
9/19/2006 - 9/26/2006
IDE is Dominant (Logical ‘0’)
RTR is Dominant (Logical ‘0’)
RB0 is Dominant (Logical ‘0’)
21.2.2 Extended Data Frame
The extended data frame begins with an SOF bit followed by a 31-bit Arbitration field as
illustrated in Figure 21-5. The Arbitration field in an extended data frame contains 29-bit identifier
in two fields separated by a Substitute Remote Request bit (SRR) and an IDE bit. The SRR bit
determines if the message is a remote frame (SRR = 1 for extended data frames). The IDE bit
indicates the data frame type. For the extended data frame, IDE = 1.
The extended data frame Control field consists of seven bits. The first bit is the RTR. For the
extended data frame, RTR = 0. The next two bits, RB1, and RB0, are reserved bits that are in
the dominant state (logic level ‘0’). The last four bits in the Control field are the DLC, which
specifies the number of data bytes present in the message.
The remaining fields in an extended data frame are identical to a standard data frame.
Figure 21-5: Format of the Extended Data Frame
9/19/2006 - 9/26/2006
Arbitration
Field
S
IDENTIFIER
O
11 Bits
F
SI
RD
RE
IDENTIFIER
18 Bits
9/19/2006 - 9/26/92/01096/2006 - 99//2169//22000066 -99/1/296/2/20000669-/199/2/260/200606- 9/26/2006
Control
Data
CRC
ACK End-of-
Field
Field
Field
Field Frame
R R R _DLC
T B B _{4 Bits}
R1 0
DATA
8 Bytes
CRC
16 Bits
ACK
2 Bits
EOF
7 Bits
IFS
3 Bits
SID10
SID1 SID0 EID17
29-bit Identifier
EID1 EID0
IDE is Recessive (Logical ‘1’)
SRR is Dominant (Logical ‘1’)
RTR is Dominant (Logical ‘0’)
RB0 is Dominant (Logical ‘0’)
RB1 is Dominant (Logical ‘0’)
© 2008-2011 Microchip Technology Inc.
DS70353C-page 21-5