gc80c520a CORERIVER Semiconductor, gc80c520a Datasheet - Page 31

• Manufacturer Part Number: gc80c520a
• Description: Midas1.0 Family Mask Rom/eprom/romless 8-bit Turbo Microcontrollers
• Manufacturer: CORERIVER Semiconductor

MiDAS1.0 Family
6.2.1.6 ESD protection of I/O ports
As electrostatic discharge (ESD) problems become more common in electronic circuits, various devices
have been used to protect circuits from ESD. All pins of MiDAS1.0 family excluding the /EA and VPP pins,
use two diodes and one resistor for ESD protection. The ESD protection scheme is shown in Figure 6-10.
Figure 6-10 ESD protection scheme I
As voltage-clamping devices, the two diodes and a resistor limit the surge voltage to a safe level for the
circuit being protected.
We protect the /EA and VPP pins from ESD with one diode and one resistor as shown in Figure 6-11
Figure 6-11 ESD protection scheme II
Similarly, the diode and the resistor limit the surge voltage to a safe level for the circuit being protected.
6.2.1.7 Output Functions
When software writes logic 0 to a port, strong pull-downs are used. However, in the case of logic 1, Port 1,
2, 3 or 4 use weak pull-up resistors and Port 0 will float (after the strong transition from 0 to 1). Thus as
long as the ports are not pulled low by another output driver, the pin status will be high. The voltage of a
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