Atmel Evaluation Kit AT91SAM9X25-EK AT91SAM9X25-EK Scheda Tecnica
Codici prodotto
AT91SAM9X25-EK
828
SAM9X25 [DATASHEET]
11054E–ATARM–10-Mar-2014
39.7.8.11 Response Data Length
The LIN response data length is the number of data fields (bytes) of the response excluding the checksum.
The response data length can either be configured by the user or be defined automatically by bits 4 and 5 of the Identifier
(compatibility to LIN Specification 1.1). The user can choose between these two modes by the DLM bit of the LIN Mode
register (US_LINMR):
(compatibility to LIN Specification 1.1). The user can choose between these two modes by the DLM bit of the LIN Mode
register (US_LINMR):
DLM = 0: the response data length is configured by the user via the DLC field of the LIN Mode register
(US_LINMR). The response data length is equal to (DLC + 1) bytes. DLC can be programmed from 0 to 255, so
the response can contain from 1 data byte up to 256 data bytes.
(US_LINMR). The response data length is equal to (DLC + 1) bytes. DLC can be programmed from 0 to 255, so
the response can contain from 1 data byte up to 256 data bytes.
DLM = 1: the response data length is defined by the Identifier (IDCHR in US_LINIR) according to the table below.
The DLC field of the LIN Mode register (US_LINMR) is discarded. The response can contain 2 or 4 or 8 data bytes.
The DLC field of the LIN Mode register (US_LINMR) is discarded. The response can contain 2 or 4 or 8 data bytes.
Figure 39-43.Response Data Length
39.7.8.12 Checksum
The last field of a frame is the checksum. The checksum contains the inverted 8- bit sum with carry, over all data bytes or
all data bytes and the protected identifier. Checksum calculation over the data bytes only is called classic checksum and
it is used for communication with LIN 1.3 slaves. Checksum calculation over the data bytes and the protected identifier
byte is called enhanced checksum and it is used for communication with LIN 2.0 slaves.
all data bytes and the protected identifier. Checksum calculation over the data bytes only is called classic checksum and
it is used for communication with LIN 1.3 slaves. Checksum calculation over the data bytes and the protected identifier
byte is called enhanced checksum and it is used for communication with LIN 2.0 slaves.
The USART can be configured to:
Send/Check an Enhanced checksum automatically (CHKDIS = 0 & CHKTYP = 0)
Send/Check a Classic checksum automatically (CHKDIS = 0 & CHKTYP = 1)
Not send/check a checksum (CHKDIS = 1)
This configuration is made by the Checksum Type (CHKTYP) and Checksum Disable (CHKDIS) fields of the LIN Mode
register (US_LINMR).
register (US_LINMR).
If the checksum feature is disabled, the user can send it manually all the same, by considering the checksum as a normal
data byte and by adding 1 to the response data length (see
data byte and by adding 1 to the response data length (see
).
39.7.8.13 Frame Slot Mode
This mode is useful only for Master nodes. It respects the following rule: each frame slot shall be longer than or equal to
TFrame_Maximum.
TFrame_Maximum.
Table 39-15. Response Data Length if DLM = 1
IDCHR[5]
IDCHR[4]
Response Data Length [bytes]
0
0
2
0
1
2
1
0
4
1
1
8
User configuration: 1 - 256 data fields (DLC+1)
Identifier configuration: 2/4/8 data fields
Sync
Break
Sync
Field
Identifier
Field
Checksum
Field
Data
Field
Data
Field
Data
Field
Data
Field