Processing Of Pins On Board; X1 And X2 Pins; Reset Pin; Port Pins - NEC 78K0S/KA1+ Preliminary User's Manual

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18.7

Processing of Pins on Board

To write the flash memory on-board, connectors that connect the dedicated flash 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.

18.7.1 X1 and X2 pins

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
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connection with the external device.

18.7.2 RESET pin

If the reset signal of the dedicated flash programmer is connected to the RESET pin that is connected to the reset
signal generator on the board, signal collision takes place. To prevent this collision, isolate the connection with the
reset signal generator.
If the reset signal is input from the user system while the flash memory programming mode is set, the flash
memory will not be correctly programmed. Do not input any signal other than the reset signal of the dedicated flash
programmer.

18.7.3 Port pins

When the flash memory programming mode is set, all the pins not used for flash memory programming enter the
same status as that immediately after reset. If external devices connected to the ports do not recognize the port
status immediately after reset, the port pin must be connected to V

18.7.4 Power supply

Connect the V
Supply AV
Figure 18-5. Signal Collision (RESET Pin)
78K0S/KA1+
Signal collision
RESET
In the flash memory programming mode, the signal output by the reset
signal generator collides with the signal output by the dedicated flash
programmer. Therefore, isolate the signal of the reset signal generator.
pin to V of the flash programmer, and the V
DD DD
with the same power supply as that in the normal operation mode.
REF
Preliminary User's Manual U16898EJ1V0UD
CHAPTER 18 FLASH MEMORY
Dedicated flash programmer
connection signal
Reset signal generator
Output pin
or V
DD
pin to V
SS
via a resistor.
SS
of the flash programmer.
SS
267