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Design Ideas |
The circuit in Figure 1 uses a PIC16C55
µP to read 10-bit binary data and
directly display the data in decimal format on three common-cathode LED
displays. If value of the data exceeds 999, the displays show three hyphens
(---) to represent overflow. The PIC16C55 has high drive capability. Each output
pin can source 20 mA and sink 25 mA; the outputs can thus directly drive the LED
display.
The output pins multiplex the display,
turning only one digit on at a time for approximately 5 msec. The 10-bit data
arrives on pins RA0 to RA3, RB0 to RB4, and RC0. The assembly program in Listing 1 arranges the
input data, converts it to three BCD codes, converts each BCD word to a
corresponding seven-segment code, and then routes the code to the output port.
The clock for the µP runs at
approximately 600 kHz with the components in
Figure 1.
(DI #1937)
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