Atmel SAM9X25, Manual

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851
11054A–ATARM–27-Jul-11
SAM9X25
851
11054A–ATARM–27-Jul-11
SAM9X25
The user can choose by the WKUPTYP bit in the LIN Mode register (US_LINMR) either to send
a LIN 2.0 wakeup request (WKUPTYP=0) or to send a LIN 1.3 wakeup request (WKUPTYP=1).
A wake-up request is transmitted by writing the Control Register (US_CR) with the LINWKUP bit
to 1. Once the transfer is completed, the LINTC flag is asserted in the Status Register (US_SR).
It is cleared by writing the Control Register (US_CR) with the RSTSTA bit to 1.
39.7.8.18 Bus Idle Time-out
If the LIN bus is inactive for a certain duration, the slave nodes shall automatically enter in sleep
mode. In the LIN 2.0 specification, this time-out is fixed at 4 seconds. In the LIN 1.3 specifica-
tion, it is fixed at 25000 Tbits.
In Slave Node configuration, the Receiver Time-out detects an idle condition on the RXD line.
When a time-out is detected, the bit TIMEOUT in the Channel Status Register (US_CSR) rises
and can generate an interrupt, thus indicating to the driver to go into sleep mode.
The time-out delay period (during which the receiver waits for a new character) is programmed
in the TO field of the Receiver Time-out Register (US_RTOR). If the TO field is programmed to
0, the Receiver Time-out is disabled and no time-out is detected. The TIMEOUT bit in US_CSR
remains to 0. Otherwise, the receiver loads a 17-bit counter with the value programmed in TO.
This counter is decremented at each bit period and reloaded each time a new character is
received. If the counter reaches 0, the TIMEOUT bit in the Status Register rises.
If STTTO is performed, the counter clock is stopped until a first character is received.
If RETTO is performed, the counter starts counting down immediately from the value TO.
39.7.9 Test Modes
The USART can be programmed to operate in three different test modes. The internal loopback
capability allows on-board diagnostics. In the loopback mode the USART interface pins are dis-
connected or not and reconfigured for loopback internally or externally.
Table 39-16. Receiver Time-out programming
LIN Specification Baud Rate Time-out period TO
2.0
1 000 bit/s
4s
4 000
2 400 bit/s 9 600
9 600 bit/s 38 400
19 200 bit/s 76 800
20 000 bit/s 80 000
1.3 - 25 000 Tbits 25 000