382
32099I–01/2012
AT32UC3L016/32/64
DLM=1: the response data length is defined by the Identifier bits according to the table below.
19.6.5.11
Checksum
The last frame field is the checksum. It is configured by the Checksum Type (LINMR.CHKTYP),
and the Checksum Disable (LINMR.CHKDIS) bits. TXRDY will not be set after the last THR data
write if enabled. Writing a one to CHKDIS will disable the automatic checksum genera-
tion/checking, and the user may send/check this last byte manually, disguised as a normal data.
The checksum is an inverted 8-bit sum with carry, either:
over all data bytes, called a classic checksum. This is used for LIN 1.3 compliant slaves, and
automatically managed when CHKDIS=0, and CHKTYP=1.
over all data bytes and the protected identifier, called an enhanced checksum. This is used
for LIN 2.0 compliant slaves, and automatically managed when CHKDIS=0, and CHKTYP=0.
19.6.5.12
Frame Slot Mode
A LIN master can be configured to use frame slots with a pre-defined minimum length. Writing a
one to the Frame Slot Mode Disable bit (LINMR.FSDIS) disables this mode. This mode will not
allow TXRDY to be set after a frame transfer until the entire frame slot duration has elapsed, in
effect preventing the master from sending a new header. The LIN Transfer Complete bit
(CSR.LINTC) will still be set after the checksum has been sent. Writing a one to CR.RSTST
clears LINTC.
Figure 19-26. Frame Slot Mode with Automatic Checksum
The minimum frame slot size is determined by TFrame_Maximum, and calculated below (all val-
ues in bit periods):
THeader_Nominal = 34
Table 19-8.
Response Data Length if DLM = 1
IDCHR[5]
IDCHR[4]
Response Data Length [bytes]
00
2
01
2
10
4
11
8
Break
Synch
Protected
Identifier
Data N
Checksum
Header
Inter-
frame
space
Response
space
Frame
Frame slot = TFrame_Maximum
Response
TXRDY
Write
THR
Write
LINID
Data 1
Data 2
Data 3
Data3
Data N-1
Data N
Frame Slot Mode
Disabled
Frame Slot Mode
Enabled
LINTC
Data 1