mcf51ac256a Freescale Semiconductor, Inc, mcf51ac256a Datasheet - Page 36

• Manufacturer Part Number: mcf51ac256a
• Description: Mcf51ac Flexis
• Manufacturer: Freescale Semiconductor, Inc

Pins and Connections
cables and the absolute value of the internal pullup device play almost no role in determining rise and fall
times on the BKGD/MS pin.
2.1.10
The V
for the ADC module.
2.1.11
The MCF51AC256 series microcontrollers support up to 69 general-purpose I/O pins, which are shared
with on-chip peripheral functions (timers, serial I/O, ADC, ACMP, etc.).
When a port pin is configured as a general-purpose output or a peripheral uses the port pin as an output,
software can select one of two drive strengths and enable or disable slew rate control. When a port pin is
configured as a general-purpose input or a peripheral uses the port pin as an input, software can enable a
pullup device. Immediately after reset, all of these pins are configured as high-impedance general-purpose
inputs with internal pullup devices disabled.
When a pin is being used as an input, an input filter is enabled that filters out high frequency transients to
prevent system noise from causing an invalid value to be read. When the TMPCLK, FTM1CLK or
FTM2CLK signals are enabled, the input filter is disabled on that particular pin. In addition, the input
filters can be disabled on the two SPI modules by clearing the SOPT2[SPI1FE] or SOPT2[SPI2FE] bits.
The input filters must be disabled to run the SPI module above 5 Mbps.
When an on-chip peripheral system is controlling a pin, data direction control bits still determine what is
read from the port data registers, even though the peripheral controls the pin direction via the pin’s output
buffer enable. For information about controlling these pins as general-purpose I/O pins, see
“Parallel Input/Output
2-10
REFH
and V
ADC Reference Pins (V
General-Purpose I/O and Peripheral Ports
To avoid extra current drain from floating input pins, the reset initialization
routine in the application program must either enable on-chip pullup devices
or change the direction of unused or non-bonded pins to outputs so they do
not float.
REFL
MCF51AC256 ColdFire Integrated Microcontroller Reference Manual, Rev. 5
Control.”
pins are the voltage reference high and voltage reference low inputs, respectively,
REFH
NOTE
, V
REFL
)
Freescale Semiconductor
Chapter 6,