Operation; Built-In Pull-Up Resistor; Driving Transistors; Port Specified As An Output Port - NEC PD78212 User Manual

8-bit single-chip microcomputer sub-series

Table of Contents

µ PD78214 Sub-Series

5.2.3 Operation

Port 0 is an output-only port.

Once port 0 is put in the output mode, the output latch becomes operable, enabling data transfer between the

output latch and accumulator according to a transfer instruction. The output latch can be loaded with any data

by a logical operation instruction. Once the output latch is loaded with some data, it retains the data until it is

loaded with other data.

If port 0 is specified to be a real-time output port, no data can be written to the output latch. However, it is possible

to read the contents of the output latch if it is in the real-time output port mode.

Port 0 has no built-in pull-up resistor.

Because port 0 has an enhanced driving capacity for the high level side of the output buffer, it can drive a transistor

directly on an active-high signal.

Fig. 5-5 shows an example of connecting a transistor to the port.

Fig. 5-4 Port Specified as an Output Port

Fig. 5-5 Example of Driving a Transistor