MAC7200 datasheet(590/976 Pages) FREESCALE

590 / 976 page

The Generic FlexCAN2 Module

MAC7200 Microcontroller Family Reference Manual, Rev. 2

512

Freescale Semiconductor

28 27

22 21 20 19

16 15

CODE

LENGTH

TIME STAMP

ID (Standard/Extended)

ID (Extended)

Data Byte 0

Data Byte 1

Data Byte 2

Data Byte 3

Data Byte 4

Data Byte 5

Data Byte 6

Data Byte 7

Figure 28-2. Message Buffer Structure

Table 28-6. Message Buffer Field Descriptions

Field

Description

CODE

Message Buffer Code. This 4-bit field can be accessed (read or write) by the CPU and by the Flexcan

module itself, as part of the message buffer matching and arbitration process. The encoding is shown in

Table 28-7 and Table 28-8. See Section 28.2.7, “Functional Description,” for additional information.

SRR

Substitute Remote Request. Fixed recessive bit, used only in extended format. It must be set to ‘1’ by the

user for transmission (Tx Buffers) and will be stored with the value received on the CAN bus for Rx

receiving buffers. It can be received as either recessive or dominant. If FlexCAN receives this bit as

dominant, then it is interpreted as arbitration loss.

0 Dominant is not a valid value for transmission in Extended Format frames

1 Recessive value is compulsory for transmission in Extended Format frames

IDE

ID Extended Bit. This bit identifies whether the frame format is standard or extended.

0 Frame format is standard

1 Frame format is extended

RTR

Remote Transmission Request. This bit is used for requesting transmissions of a data frame. If FlexCAN

transmits this bit as ‘1’ (recessive) and receives it as ‘0’ (dominant), it is interpreted as arbitration loss. If

this bit is transmitted as ‘0’ (dominant), then if it is received as ‘1’ (recessive), the FlexCAN module treats

it as bit error. If the value received matches the value transmitted, it is considered as a successful bit

transmission.

0 Indicates the current MB has a Data Frame to be transmitted

1 Indicates the current MB has a Remote Frame to be transmitted

LENGTH

Length of Data in Bytes. This 4-bit field is the length (in bytes) of the Rx or Tx data, which is located in

offset $8 through $F of the MB space (see Figure 28-2). In reception, this field is written by the FlexCAN

module, copied from the DLC (Data Length Code) field of the received frame. In transmission, this field

is written by the CPU and corresponds to the DLC field value of the frame to be transmitted. When RTR=1,

the Frame to be transmitted is a Remote Frame and does not include the data field, regardless of the

Length field.

TIME STAMP Free-Running Counter Time Stamp. This 16-bit field is a copy of the Free-Running Timer, captured for Tx

and Rx frames at the time when the beginning of the Identifier field appears on the CAN bus.

Frame Identifier. In Standard Frame format, only the 11 most significant bits (28 to 18) are used for frame

identification in both receive and transmit cases. The 18 least significant bits are ignored. In Extended

Frame format, all bits are used for frame identification in both receive and transmit cases.

DATA

Data Field. Up to eight bytes can be used for a data frame. For Rx frames, the data is stored as it is

received from the CAN bus. For Tx frames, the CPU prepares the data field to be transmitted within the

frame.

MAC7200 Datasheet(PDF) 590 Page - Freescale Semiconductor, Inc

MAC7200 Datasheet(HTML) 590 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL