4coder-non-source/test_data/lots_of_files/systemTimer.s

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2023-09-30 01:17:40 +00:00
/******************************************************************************
* systemTimer.s
* by Alex Chadwick
*
* A sample assembly code implementation of the OK05 operating system.
* See main.s for details.
*
* systemTime.s contains the code that interacts with the system timer.
******************************************************************************/
/*
* The system timer runs at 1MHz, and just counts always. Thus we can deduce
* timings by measuring the difference between two readings.
*/
/*
* GetSystemTimerBase returns the base address of the System Timer region as a
* physical address in register r0.
* C++ Signature: void* GetSystemTimerBase()
*/
.globl GetSystemTimerBase
GetSystemTimerBase:
ldr r0,=0x20003000
mov pc,lr
/*
* GetTimeStamp gets the current timestamp of the system timer, and returns it
* in registers r0 and r1, with r1 being the most significant 32 bits.
* C++ Signature: u64 GetTimeStamp()
*/
.globl GetTimeStamp
GetTimeStamp:
push {lr}
bl GetSystemTimerBase
ldrd r0,r1,[r0,#4]
pop {pc}
/*
* Wait waits at least a specified number of microseconds before returning.
* The duration to wait is given in r0.
* C++ Signature: void Wait(u32 delayInMicroSeconds)
*/
.globl Wait
Wait:
delay .req r2
mov delay,r0
push {lr}
bl GetTimeStamp
start .req r3
mov start,r0
loop$:
bl GetTimeStamp
elapsed .req r1
sub elapsed,r0,start
cmp elapsed,delay
.unreq elapsed
bls loop$
.unreq delay
.unreq start
pop {pc}