MC68HC05PV8 Datasheet, PDF (105/196 Pages) Freescale Semiconductor, Inc – Techinal Data - rev 1.9

Freescale Semiconductor, Inc.
Input/Output Ports
Port C (High Voltage Port)
CSDT
Interrupt
PC4
DDR
DATA
VSS
Figure 7-11 PC4 Circuitry 68HC05PV8A
Port pin PC0 comprises a circuit that senses the outside resistance R_PIN
to VSUP. PC4 has a different circuit, which senses the outside
resistance R_PIN to VSS (only on 68HC(8)05PV8). PC1, PC2 and PC3
have an universal one, which senses the outside resistance either to
VSS or to VSUP, depending on the state of the corresponding data
register bit.
The contact sense circuitry is enabled by setting the corresponding bits
PC4CS, PC3CS, PC2CS, PC1CS or PC0CS of the port C configuration
register to 1. In addition, the pin has to be configured as an output by
setting the corresponding DDR bit to 1 and the data bit to 0 (for R_PIN to
VSUP, e.g. external switch to VSUP) or to 1 (for R_PIN to VSS, e.g.
external switch to VSS). If the outside resistance R_PIN is lower than the
specified value, the contact sense circuitry interprets this as a logical 1.
The principal sense characteristic is given in Figure 7-12. The result of
this sense operation is given by the bits CSD4, CSD3, CSD2, CSD1 and
CSD0 of the port C status register.
MC68HC(8)05PV8/A — Rev. 1.9
Input/Output Ports
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Technical Data