R01UH0823EJ0100 Rev.1.00
Page 99 of 1823
Jul 31, 2019
RX23W Group
3. Operating Modes
3.3
Details of Operating Modes
3.3.1
Single-Chip Mode
In this mode, all I/O ports can be used as general input/output ports, peripheral function input/output, or interrupt input
pins.
The chip starts up in single-chip mode if the high level is on the MD pin on release from the reset state.
3.3.2
Boot Mode
In this mode, the on-chip flash memory modifying program (boot program) stored in a dedicated area within the MCU
operates. The on-chip flash memory (ROM and E2 DataFlash) can be modified from outside the MCU by using a USB or
universal asynchronous receiver/transmitter (SCI1). For details, see
section 50, Flash Memory (FLASH)
.
When a reset is released while the MD pin is low, boot mode is selected.
3.3.2.1
Boot Mode (USB Interface)
When a reset is released while the MD pin is low and the UB pin is high, boot mode (USB interface) is selected. For
details on boot mode (USB interface), refer to
section 50.8.1, Boot Mode (USB Interface)
3.3.2.2
Boot Mode (SCI)
When a reset is released while the MD pin is low and the UB pin is low, boot mode (SCI) is selected. For details on boot
mode (SCI), refer to