UPD78F0138 NEC, UPD78F0138 Datasheet - Page 450

• Manufacturer Part Number: UPD78F0138
• Description: (UPD78xxxx) 8-Bit Single-Chip Microcontrollers
• Manufacturer: NEC

(1) Signal collision
(2) Malfunction of other device
450
If the dedicated flash programmer (output) is connected to a pin (input) of a serial interface connected to another
device (output), signal collision takes place. To avoid this collision, either isolate the connection with the other
device, or make the other device go into an output high-impedance state.
If the dedicated flash programmer (output or input) is connected to a pin (input or output) of a serial interface
connected to another device (input), a signal may be output to the other device, causing the device to
malfunction. To avoid this malfunction, isolate the connection with the other device.
PD78F0134, 78F0138
PD78F0134, 78F0138
PD78F0134, 78F0138
Input pin
Figure 27-15. Signal Collision (Input Pin of Serial Interface)
Pin
Pin
In the flash memory programming mode, the signal output by the device
collides with the signal sent from the dedicated flash programmer.
Therefore, isolate the signal of the other device.
If the signal output by the
programming mode affects the other device, isolate the signal of the other
device.
If the signal output by the dedicated flash programmer in the flash memory
programming mode affects the other device, isolate the signal of the other
device.
Figure 27-16. Malfunction of Other Device
CHAPTER 27
Signal collision
User’s Manual U16228EJ2V0UD
µ
PD78F0134, 78F0138
PD78F0134 or 78F0138 in the flash memory
Dedicated flash programmer
connection pin
Dedicated flash programmer
connection pin
Dedicated flash programmer
connection pin
Other device
Other device
Other device
Output pin
Input pin
Input pin