Memory Mapped Input/Output Flashcards
Memory contains
flash memory
RAM
other flash/RAM
what connects the processsing unit and memory device
the memory bus
how many memory buses are there
one, this means that the processing unit can only communicate with one memory device ata time
what are the three parts of the memory bus
control bus
data bus
address bus
what does the control bus do
controls communication between the processing unit and memory device
what does the address bus do
carries the address of the location we want to store the data in/load the data from
how many electronic connections are in the address bus, why
32 electronic connections
1 for each bit of the address were looking to store.load
can memory devices overlap when assigned space in memory
no
what does GPIO stand for
general purpose input/output
do microcontrollers include both microprocessors and peripherals
yes, system on chip
what instructions are used to communicate between peripherals and processor
ldr and str
some of the peripherals on our microprocessor include
flash memory RAM USB Ethernet Timers GPIO
what is the sysTick timer
a timer integrated into the ARM coretx m4
what value does the systick timer begin counting down from
the value that is loaded into it
when the systick timer reaches 0 what happens
it resets and restarts counting down again from the load value
why does the sysTick timer count down in miliseconds and not seconds
it only takes in a 24 bit value and this isn’t big enough for 1 second
what does CSR stand for
control and status register
the bit 0 is the CSR is used to what
enable and disable the timer
bit 1 in the CSR is used for what
enable and disable the timer interrupt
bit 2 in the CSR is used for wha
clock source
bit 3 in the CSR is used for what
reads as 1 if the timer has reached 0 since the last time we read it
when read itll be set to 0
how to reset teh internal counter to 0
write any value to the value register
what does the value register do
timer counter
what is polling
repeatedly reading the value in the systick timer until it reaches 0 and then stopping the subroutine
what does the syntax 0b1«13 mean
binary shifted left by 13 bits
makes a 1 in position 13 and 0s everywhere else
what is an interrupt
they interrupt the current program when some external device tells it to, beginning another program, executing it and returning to the current program once complete
what are exceptions
events outside the normal flow of the program, can occur at unpredictable times
examples of exceptions
processor fetches the next address from memory but its not a valid instruction
timer completes counting down
trying str to a ROM address
what is a non maskable interrupts
the system cannot configure itself to ignore these interrupts
what is a hard fault
arise during the handling of another exception
when do memManage and bus faults occur
when trying to load and store from memory and something goes wrong
what is a usage fault
trying to run an execution that cannot be run
how to hide the side effects of an exception subroutine
acknowledge it at the end of the subroutine
how do exceptions raised know which exception subroutine to go to
using the exception vector table
what does FTSR stand for
falling trigger selection register
