How to make on board debug V1.1
Chapter 4 Hardware Design
MCU-AN- 500018-E-11 – Page 9
4.2 Dual Flash MCU Debugging Circuit
Figure 4-3 shows the circuit diagram of the in-system debugging interface. To design the in-
system debugging interface, three pins, UVCC_EV, GND and DBG, are needed. (Add pin
RST_OUT if necessary.)
Figure 4-3 Dual Flash MCU Debugging Circuit
Component Recommendation:
D1: VF < 0.3V when IF = 1mA. E.g. LL103A, 1SS294.
Below is a list of functions of the interface connector.
(1) J1 is a 10-pin connector, used as the interface of this circuit.
(2) The write voltage (VCC = 4.5V to 5.5V) is supplied from the user system. The UVCC_EV
and DBG pins control the PGM mode entry.
(3) Pin 2 of the connector connects to the GND.
(4) The DBG pin provides 1-line UART communication with the debugger. Serial write mode
can be set by providing special timing of DBG and VCC pins.
If the MCU target need a reset circuit, and please design a reset circuit as follow circuit.
Figure 4-4 In-system Debugger Interface
Pin 4 of the connector is used to connect to the reset circuit. Design a switch K1 between the
reset circuit and the reset pin (RSTX). When debugging operation is over, K1 can be
switched on to supply the reset circuit to the target MCU.
Target Board
Target Board
