UPD78F9500MA-CAC-A Datasheet, PDF (231/342 Pages) Renesas Technology Corp – 8-Bit Single-Chip Microcontrollers

CHAPTER 16 FLASH MEMORY
16.6 Processing of Pins on Board
To write the flash memory on-board, connectors that connect the dedicated flash memory programmer must be
provided on the target system. First provide a function that selects the normal operation mode or flash memory
programming mode on the board.
When the flash memory programming mode is set, all the pins not used for programming the flash memory are in
the same status as immediately after reset. Therefore, if the external device does not recognize the state immediately
after reset, the pins must be processed as described below.
The state of the pins in the self programming mode is the same as that in the HALT mode.
16.6.1 X1 and X2 pins (μPD78F920x)
The X1 and X2 pins are used as the serial interface of flash memory programming. Therefore, if the X1 and X2
pins are connected to an external device, a signal conflict occurs. To prevent the conflict of signals, isolate the
connection with the external device.
When connected a capacitor to X1 and X2 pins, waveform at the time of communication is changed. Therefore
there is a possibility that cannot communicate depending on capacitor capacitance. When perform flash memory
programming, isolate connection with a condenser.
Perform the following processing (1) and (2) when on-board programming is performed with the resonator mounted,
when it is difficult to isolate the resonator, while a crystal or ceramic resonator is selected as the system clock.
(1) Mount the minimum-possible test pads between the device and the resonator, and connect the flash memory
programmer via the test pad. Keep the wiring as short as possible (refer to Figure 16-4 and Table 16-3).
(2) Set the oscillation frequency of the communication clock for writing using the programming GUI of the
dedicated flash memory programmer. Research the series/parallel resonant and antiresonant frequencies of
the resonator used, and set the oscillation frequency so that it is outside the range of the resonant frequency
±10% (refer to Figure 16-5 and Table 16-4).
Figure 16-4. Example of Mounting Test Pads
Test pad
VSS X1
X2
Table 16-3. Clock to Be Used and Mounting of Test Pads
Clock to Be Used
High-speed internal oscillation clock
External clock
Crystal/ceramic oscillation
clock
Before resonator is mounted
After resonator is mounted
Mounting of Test Pads
Not required
Required
User’s Manual U18172EJ3V0UD
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