Renesas RL78 - Specification

RL78/G11 UART Reception in STOP Mode Using Middle-speed On-chip Oscillator IAR
R01AN3634EJ0100 Rev.1.00 Page 3 of 85
Feb. 15, 2017
1. Specification
The RL78/G11 middle-speed on-chip oscillator can be used to receive data in UART communications during STOP
mode. When the INTP (external interrupt) pin detects the start bit during STOP mode, STOP mode is released.
Operations return from STOP mode and UART data is received simultaneously.
The serial array unit (SAU) is only used for receiving UART communication.
The timer array unit (TAU) is used to correct the baud rate. The external interrupt edge detection 11 (INTP11)
interrupt is used to return the CPU from STOP mode
An LED lamp indicates whether the data from the targeted communication device was successfully received or an error
occurred.
The middle-speed on-chip oscillator does not provide frequency accurate enough for UART communications and baud
rate corrections are necessary. A detailed description on how to correct the baud rate is provided in the following
document: “RL78/G11 UART communication with middle speed on chip oscillator IAR (R01AN3621EJ).”
Note: When using the middle-speed on-chip oscillator, UART data cannot be received during STOP mode if the
SNOOZE mode is in use. To do, please use the high-speed on-chip oscillator.
Table 1.1 shows peripheral functions and usages. Figure 1.1 shows an outline of the application.
Table 1.1 Peripheral functions and usages
Peripheral functions Usage
Serial array unit (SAU) UART receive (UART0)
External interrupt (INTP) Start bit detection
Timer array Unit (TAU)
Middle-speed on-chip oscillator frequency
measurement
Figure 1.1 Application Outline
Detects start bit edge with external interrupt pin, returns
operations from STOP mode and received UART data.