ATmega16HVB datasheet(138/273 Pages) ATMEL

138 / 273 page

138

8042A–AVR–07/09

ATmega16HVB/32HVB

The user must disable the External Protection Input in the BPCR register before the port can be

used as a normal port.

Also during the reset sequence, the External Protection Input may disable the FETs. Conse-

quently, if the External Protection feature is not used and DUVR mode is enabled in reset, the

External Protection input must be held low until disabled by SW.

It is recommended that the external interrupt on the External Protection Input port is configured

to ‘any edge’ to generate an interrupt to the microcontroller when using this feature, indicating

that the FET protection status has changed. By reading the pin register, the External Protection

status can be determined. If the pin register is set, it means that External Protection is trigged

and the FET control signals in FCSR (CFE, DFE and DUVRD) are overridden and the FETs are

disabled. In the opposite case, External Protection violation is not present.

To ensure a safe exit from the External Protection Input condition, the FETs and DUVR mode

should be disabled by SW when an External Protection condition is detected. This enables soft-

ware to completely control when the FETs are switched ON again.

Short pulses on the EXTPROT pin, for instance caused by temporary high voltages on the BATT

pin when connecting a charger, may trigger the External Protection Input (refer to ”Operating

Circuit” on page 225). However if the SW does not take any action, the C-FET and D-FET will be

re-enabled automatically once the External Protection condition disappears.

Figure 24-1. External Protection Input example.

FC SR [C FE ]

FC SR [D FE ]

PC 0

IN T 0

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