598
SAM9G45 [DATASHEET]
6438K–ATARM–12-Feb-13
Figure 33-54. Slave Node with PDC
33.7.8.25
Wake-up Request
Any node in a sleeping LIN cluster may request a wake-up.
In the LIN 2.0 specification, the wakeup request is issued by forcing the bus to the dominant state from 250 μs to 5
ms. For this, it is necessary to send the character 0xF0 in order to impose 5 successive dominant bits. Whatever
the baud rate is, this character respects the specified timings.
Baud rate min = 1 kbit/s -> Tbit = 1ms -> 5 Tbits = 5 ms
Baud rate max = 20 kbit/s -> Tbi t= 50 μs -> 5 Tbits = 250 μs
In the LIN 1.3 specification, the wakeup request should be generated with the character 0x80 in order to impose 8
successive dominant bits.
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 at 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 at 1.
33.7.8.26
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 specification, 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 at 0, the Receiver Time-out is disabled
and no time-out is detected. The TIMEOUT bit in US_CSR remains at 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.
|
DATA 0
DATA N
PDC
(DMA)
RXRDY
USART3
LIN CONTROLLER
APB bus
READ BUFFER
NACT = SUBSCRIBE
DATA 0
DATA N
PDC
(DMA)
TXRDY
USART3
LIN CONTROLLER
APB bus
WRITE BUFFER