MC68HC05PV8 Datasheet, PDF (106/196 Pages) Freescale Semiconductor, Inc – Techinal Data - rev 1.9

Technical Data
Freescale Semiconductor, Inc.
Contact Sense
1
Data Bit
CSD4–0
0
Outside Resistance
Figure 7-12 Principal Characteristic of the Contact Sense Circuitry
When setting PCXCS and clearing the corresponding DDR bit, the
signal generated by the high voltage input block is used instead of
the one of the contact sense block to drive the CSD bits. The CSD
bits will in this case reflect a logical 1 if the corresponding input
voltage is below HV_IL, and a logical 0 if the input voltage is above
HV_IH.
A contact sense interrupt is generated if the status of any CSD bit
changes with the corresponding PCXCS bit set. The interrupt trigger
occurs on both edges of the CSD bit change and sets the CSIF flag in
the port C status register.
The interrupt can be masked by the CSIE bit of the port C configuration
register.
An external resistor has to be placed in serial to PC0-4 because of two
reasons:
• limit internal power dissipation,
• internal substrate current injection may occur if the pin voltage is
out of the supply voltage range.
7.6.4 Port C ISO9141 Interface
To use Port C4 as an ISO9141 physical interface, Port C4 must be
always programmed as an output. This automatically enables the
biasing circuit for the ISO9141 driver. Furthermore, the ISOM bit in the
Port C Configuration Register 0 has to be set. This driver incorporates
an overcurrent limitation circuit. Because of excessive power dissipation
Technical Data
MC68HC(8)05PV8/A — Rev. 1.9
Input/Output Ports
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