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8xC196EA microcontroller user's manual.1998.pdf
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USING THE TEST-ROM ROUTINES

17.3 ENTERING TEST-ROM ROUTINES

To execute properly, the microcontroller must have these minimum hardware connections: XTAL1 driven, unused input pins strapped, and power and grounds applied. Follow the operating conditions specified in the datasheet. Place the device into test-ROM mode by configuring pins as described in Tables 17-1 and holding those values during the rising edge of RESET#.

17.3.1 Power-up and Power-down Sequences

To enter a test-ROM routine, follow these power-up and power-down procedures.

WARNING

Failure to observe these precautions will cause permanent device damage.

Ensure that the port 12 pins are in their desired states before RESET# rises.

Ensure that all voltages are within the ranges specified in the datasheet and that the oscillator is stable before RESET# rises.

Ensure that the power supplies to the VCC, EA# and RESET# pins are well regulated and free of glitches and spikes.

Ensure that all VSS pins are well grounded.

17.3.1.1Power-up Sequence

1.Hold RESET# low while VCC stabilizes.

2.While VCC is ramping to within specifications, ensure that no pins are driven higher than VCC + 0.5 volts.

3.Ensure that all pins needed to enter the desired mode are driven to the correct values (Table 17-1).

4.After the oscillator stabilizes, bring the RESET# pin high.

17.3.1.2Power-down Sequence

1.Assert the RESET# signal and hold it low throughout the powerdown sequence.

2.Turn off the VCC supply and allow time for it to reach 0 volts.

17-5

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