MC9S12UF32 Card Reader Reference Design User Manual, Rev. 0.1
Freescale Semiconductor
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pulse-width
— The amount of time a signal is on as opposed to being in its off state.
pulse-width modulation (PWM)
— Controlled variation (modulation) of the pulse width of a signal with
a constant frequency.
push
— An instruction that copies the contents of the accumulator to the stack RAM. The stack RAM
address is in the stack pointer.
PWM period
— The time required for one complete cycle of a PWM waveform.
RAM
— Random access memory. All RAM locations can be read or written by the CPU. The contents of
a RAM memory location remain valid until the CPU writes a different value or until power is turned
off.
RC circuit
— A circuit consisting of capacitors and resistors having a defined time constant.
read
— To copy the contents of a memory location to the accumulator.
register
— A circuit that stores a group of bits.
reserved memory location
— A memory location that is used only in special factory test modes. Writing
to a reserved location has no effect. Reading a reserved location returns an unpredictable value.
reset
— To force a device to a known condition.
SCI
— See “serial communication interface module (SCI).”
serial
— Pertaining to sequential transmission over a single line.
serial communications interface module (SCI)
— A module that supports asynchronous
communication.
serial peripheral interface module (SPI)
— A module that supports synchronous communication.
set
— To change a bit from logic 0 to logic 1; opposite of clear.
shift register
— A chain of circuits that can retain the logic levels (logic 1 or logic 0) written to them and
that can shift the logic levels to the right or left through adjacent circuits in the chain.
signed
— A binary number notation that accommodates both positive and negative numbers. The most
significant bit is used to indicate whether the number is positive or negative, normally logic 0 for
positive and logic 1 for negative. The other seven bits indicate the magnitude of the number.
software
— Instructions and data that control the operation of a microcontroller.
software interrupt (SWI)
— An instruction that causes an interrupt and its associated vector fetch.
SPI
— See “serial peripheral interface module (SPI).”
stack
— A portion of RAM reserved for storage of CPU register contents and subroutine return
addresses.
stack pointer (SP)
— A 16-bit register in the CPU containing the address of the next available storage
location on the stack.
