MC68HC705JP7 Datasheet, PDF (105/242 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Parallel Input/Output
Port Transitions
7.6 Port Transitions
Glitches and temporary floating inputs can occur if the control bits
regarding each port I/O pin are not performed in the correct sequence.
• Do not use read-modify-write instructions on pulldown register A
or B.
• Avoid glitches on port pins by writing to the port data register
before changing data direction register bits from a logic 0 to a
logic 1.
• Avoid a floating port input by clearing its pulldown register bit
before changing its data direction register bit from a logic 1 to a
logic 0.
• The SWPDI bit in the MOR turns off all port pulldown devices and
disables software control of the pulldown devices. Reset has no
effect on the pulldown devices when the SWPDI bit is set.
• Two or more output pins of the same port can be connected
electrically to provide output currents up to the sum of the
maximum specified drive currents as defined in 15.8 DC
Electrical Characteristics (5.0 Vdc) and 15.9 DC Electrical
Characteristics (3.0 Vdc). Care must be taken to ensure that all
ganged pins always maintain the same output logic value.
MC68HC705JJ7 • MC68HC705JP7 — REV 4
MOTOROLA
Parallel Input/Output
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