RL78/F13, F14 CHAPTER 17 LIN/UART MODULE (RLIN3)
R01UH0368EJ0210 Rev.2.10 1233
Dec 10, 2015
(5) SNOOZE Mode Function
The LIN/UART module (UART mode) is provided with SNOOZE mode during reception. The SNOOZE mode allows data
reception without CPU operation when the LRXDn pin input is detected in STOP mode.
To use the LIN/UART module (UART mode) in SNOOZE mode, make the following settings before entering STOP mode.
In SNOOZE mode, it is necessary to set the different baud rate for UART reception from that in normal operation. Refer
to tables 17-21 to 17-24 and set the LBRPn register and LPRS[2:0] bits and NSPB[3:0] bits in the LWBRn register
appropriately.
Set the UWC bit in the UART standby control register (LUSCn). Also set the USEC and URDCC bits in the LUSCn
register to enable or disable error interrupt generation upon occurrence of a communication error and comparison of
the received data and the LIDBn register value, respectively.
Set the UROE bit to 1 in the UART operation enable register (LUOERn) immediately before entering STOP mode.
After entering STOP mode, UART reception starts upon detection of the LRXDn edge (start bit input).
Cautions 1. SNOOZE mode can be set only when the LINnMCK bit in the LINCKSEL register is 0 (f
CLK
selected)
and the high-speed on-chip oscillator clock (f
IH
) is selected for f
CLK
.
2. The maximum transfer rate in SNOOZE mode is 4800 bps when the FRQSEL4 in the user option
byte (000C2H/020C2H) is set to 0, and 2400 bps when FRQSEL4 is set to 1.
3. With UWC = 1, the UART can be used only if reception is started during STOP mode.
If another SNOOZE function or interrupt is also used and reception is started during any state other
than STOP mode as described below, data is not received correctly and a framing error or parity
error may occur.
After setting UWC to 1, reception is started before entering STOP mode.
Reception is started during another SNOOZE mode.
After returning to normal operation from STOP mode upon an interrupt or other cause,
reception is started before setting UWC to 0.
4. With USEC = 1, if an error (parity error or framing error) or change in status (detection of the
expansion bit) is detected in SNOOZE mode, the flag is not set to 1 thus generating no error
interrupt.
To Next Page
Loading...
Need help?
General
