MC68HC705JJ7 Datasheet, PDF (69/164 Pages) Freescale Semiconductor, Inc – Microcontrollers

Port Transitions
Table 7-4. Port C Pin Functions (28-Pin Versions Only)
Port C
Pin(s)
SWPDI
in MOR
Control Bits
Port C
PDICH PDICL
DDRCx⁽¹⁾
0
X⁽²⁾
0
0
PC0
PC1
0
X⁽²⁾
1
0
PC2
1
X
X⁽²⁾
0
PC3
X⁽²⁾
X⁽²⁾
X⁽²⁾
1
0
PC4
PC5
0
0
X⁽²⁾
0
1
X⁽²⁾
0
PC6
1
X
X⁽²⁾
0
PC7
X⁽²⁾
X⁽²⁾
X⁽²⁾
1
1. DDRC can always be read or written.
2. Don’t care
PORTC Access
(Pin or Data Register)
Read
Pin
Write
Data
Pin
Pin
Data
Pin
Pin
Pin
Data
Data
Data
Data
Data
Data
Data
Data
Result on
Port C Pins
Pulldown
On
Pin
PCx in
Off
PCx in
Off
PCx in
Off
PCx out
On
PCx in
Off
PCx in
Off
PCx in
Off
PCx out
7.5 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 15.7 DC Electrical
Characteristics (5.0 Vdc) and 15.8 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 Advance Information Data Sheet, Rev. 4.1
Freescale Semiconductor
69