R01UH0823EJ0100 Rev.1.00
Page 1701 of 1823
Jul 31, 2019
RX23W Group
50. Flash Memory (FLASH)
50.8.1
Boot Mode (USB Interface)
The flash memory can be programmed and erased using the USB interface in boot mode (USB interface). The user
area and data area can be rewritten.
When a reset is released while the MD pin is low and the UB pin is high, the MCU starts in boot mode (USB interface).
Self-powered or bus-powered can be selected in accordance with the state of the UPSEL pin. When a reset is released
while the UPSEL pin is low, self-powered mode is selected. When a reset is released while the UPSEL pin is high, bus-
powered mode is selected.
Contact the manufacturer for details on the serial programmer (USB programmer).
50.8.1.1
Operating Conditions in Boot Mode (USB Interface)
USB0 is used for communication with the serial programmer in boot mode (USB interface).
4, 6, 8, 12, or 16 MHz can be used as the frequency input to the main clock oscillator. The operating voltage range is
between 3.0 V and 3.6 V.
Connect the UB pin to VCC directly or VCC via a resistor (pull up).
shows an Example of Pin Connections in Boot Mode (USB Interface) When Self-Powered.
lists Pin Handling in Boot Mode (USB Interface) When Self-Powered.
Connections in Boot Mode (USB Interface) When Bus-Powered.
lists Pin Handling in Boot Mode (USB
Interface) in Bus-Powered Mode.
Examples of pin connections shown in
are simplified circuits. Operations are not
guaranteed in all systems.
Figure 50.22
Example of Pin Connections in Boot Mode (USB Interface) When Self-Powered
MCU
VCC
USB0_VBUS
VCC_USB
UPSEL
RES#
UB
USB0_DP
XTAL
USB0_DM
EXTAL
VCL
VSS_USB
MD
VSS
Reset circuit
(user logic)
Connection/disconnection
detection signal input
Data I/O
Data I/O
*1
*2
Note 1. Connect a 4, 6, 8, 12, or 16 MHz crystal, ceramic resonator or oscillator to the main clock oscillator.
Note 2. UPSEL is assigned to the same pin as NMI. This is an example when the falling edge is selected by the NMI
detection set bit.