Cypress FR81S CY91F52 Series Recommendation For Hardware Setup page 26

The setting of the Mode pins can be done automatically by the programming system as you can see in the Figure 31,
using only one signal connected to pin MD0, inverting MD1 and a pull-up resistor on the pin P006.
Flash Programming System
R10
R11
Closed
Serial
Programming Mode
Open
User/Run Mode
Reset
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Figure 31. Principal Schematic for serial programming via Usart0
ECU
GND
GND GND
Document No. 002-09375 Rev. *B
Recommendation for Hardware Setup 32-Bit FR81S Family
VCC
R7
T1
R8
GND
MCU
SOT0_0
SIN0_0
P006
MD1
MD0
RSTX
C1
GND
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