Hardware Reference
In-Depth Information
Output handshake A protocol that uses two handshake signals to make sure that an output
device correctly receives the data driven by the peripheral chip (sent by the CPU).
Output port The part of the circuit in a microcontroller that consists of output pins, data
register, and control circuitry to send data to the output device.
Overflow A condition that occurs when the result of an arithmetic operation cannot be
accommodated by the preset number of bits (say, 8 or 16 bits); it occurs fairly often when
numbers are represented by fixed numbers of bits.
Parameter passing The process and mechanism of sending parameters from a caller to a
subroutine, where they are used in computations; parameters can be sent to a subroutine
using CPU registers, the stack, or global memory.
Parity error An error in which an odd number of bits change value; it can be detected by a
parity checking circuit.
Phase_seg1 and Phase_seg2 Segments that are used to compensate for edge phase errors.
These segments can be lengthened or shortened by synchronization.
Physical layer The lowest layer in the layered network architecture. This layer deals
with how signals are transmitted, the descriptions of bit timing, bit encoding, and
synchronization.
Physical time In the HCS12 timer system, the time represented by the count in the 16-bit
main timer counter.
Point-to-point A data communication scheme in which two stations communicate as peers.
Precedence of operators The order in which operators are processed.
Program A set of instructions that the computer hardware can execute.
Program counter (PC)
A register that keeps track of the address of the next instruction to be
executed.
Program loops
A group of instructions or statements that are executed by the processor more
than once.
PROM (programmable read-only memory) A type of ROM that allows the end user to
program it once and only once using a device called a PROM programmer.
Prop_seg The segment within a bit time used to compensate for the physical delay times
within the CAN network.
Pseudo-code An expressive method that combines the use of plain English and statements
similar to certain programming languages to represent an algorithm.
Pull The operation that removes the top element from a stack data structure.
Pulse accumulator A timer function that uses a counter to count the number of events that
occur or measure the duration of a single pulse.
Pulse-width modulation A timer function that allows the user to specify the frequency and
duty cycle of the digital waveform to be generated.
Push The operation that adds a new element to the top of a stack data structure.
Queue A data structure to which elements can be added at only one end and removed from
only the other end. The end to which new elements can be added is called the tail of the
queue, and the end from which elements can be removed is called the head of the queue.
Random-access memory (RAM) RAM allows read and write access to every location inside
the memory chip. Furthermore, read access and write access take the same amount of time
for any location within the RAM chip.
Receiver overrun A data communication error in which a character or a number of characters
were received but not read from the buffer before subsequent characters are received.
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