mc68hc05pv8a Freescale Semiconductor, Inc, mc68hc05pv8a Datasheet - Page 106

• Manufacturer Part Number: mc68hc05pv8a
• Description: Mc68hc05pv8a Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Technical Data
7.6.4 Port C ISO9141 Interface
Technical Data
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
HV
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:
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
Figure 7-12 Principal Characteristic of the Contact Sense Circuitry
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Freescale Semiconductor, Inc.
IH
.
For More Information On This Product,
limit internal power dissipation,
internal substrate current injection may occur if the pin voltage is
out of the supply voltage range.
Contact Sense
Data Bit
CSD4–0
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Input/Output Ports
IL
, and a logical 0 if the input voltage is above
0
1
Outside Resistance
MC68HC(8)05PV8/A — Rev. 1.9