RL78/G11 UART Reception in STOP Mode Using Middle-speed On-chip Oscillator IAR
R01AN3634EJ0100 Rev.1.00 Page 16 of 85
Feb. 15, 2017
5.3 UART How to Receive UART Data in STOP Mode
Generally, when MOCO (middle-speed on-chip oscillator) is selected as the system clock, the UART receive operation
is disabled if the program is stopped due to SNOOZE mode.
However, the UART receive operation can be enabled when MOCO is selected as the system clock by skipping
SNOOZE mode and, instead, returning directly from STOP mode. To do so, you will need to release STOP mode by
connecting the external interrupt pin (INTPn) to the RxD pin and detecting the start bit with the external interrupt pin.
Figure 5.3 shows the flow for enabling the UART receive operation in STOP mode.
Start setup
Write 1 to STmn bit
→ SEmn = 0
Stop operations of u nu sed cha nn el s to shift
to STOP mode.
All channels
TSFmn=0?
SAU initialization
SSCm register setting
(SWCm = 0)
Write 1 to SSm1 bit
→ SEm1 = 1
Enable interrupt
Shift to STOP mode
Set channel 1 for UART reception.
Do not use SNOOZE mode functions.
Communication wait state
Clear used interrupt request flags and
release INTPn interrupt mask.
The setup is basically the same as that of UART reception
in SNOOZE mode.
Please set SWCm bit to 0 and do not use SNOOZE mode
functions.
After completing UART reception setup, release the
INTPn interrupt mask, enable standby release signal
generation by start bit edge, and shift to STOP mode.
Figure 5.3 How to Receive UART Data in STOP Mode
5.4 Optional Byte Settings
Table 5.3 shows the list of settings for optional bytes.
Table 5.3 Optional Byte Settings
Address Setting Description
000C0H/010C0H 1110 1111B Watchdog timer operation disabled
(stop count after reset release)
000C1H/010C1H 0111 1111B LVD reset mode, 2.81V(2.76 to 2.87V)
000C2H/010C2H 1110 0000B HS mode, HOCO: 24MHz
000C3H/010C3H 1000 0100B Enables the on-chip debugging
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