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| author | Silvan Jegen <s.jegen@gmail.com> | 2019-08-24 16:40:43 +0200 |
|---|---|---|
| committer | Silvan Jegen <s.jegen@gmail.com> | 2019-08-24 16:40:43 +0200 |
| commit | c3afc9768d110c4dbaa2f0133a3a77167f1f2293 (patch) | |
| tree | 34fee88e9b92d55870e56fcd3b0bbe7ac9849fac | |
| parent | 6502be88d94aa1d5e3949832c12f47deb8329a4c (diff) | |
delay: load/write high and low value
I don't think this should make a difference in practice.
| -rw-r--r-- | software/first/delay.S | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/software/first/delay.S b/software/first/delay.S index 656625f..039d924 100644 --- a/software/first/delay.S +++ b/software/first/delay.S @@ -4,20 +4,22 @@ .include "memory_map.inc" -# a0 is delay in milliseconds argument +# a0 is delay-in-milliseconds argument delay: addi sp, sp, -16 # Allocate stack frame sw ra, 12(sp) # save return address to the stack li t0, MTIME # load the timer register - lw t1, 0(t0) # load value of the timer + lw t1, 0(t0) # load low value of the timer + lw t2, 4(t0) # load high value of the timer - li t2, MTIME_FREQUENCY # get clock freq (approx.) - mul t2, t2, a0 # multiply milliseconds with freq - add t2, t1, t2 # target mtime is now in t2 - li t3, MTIMECMP # load address of MTIMECMP register - sw t2, 0(t3) # store target time to MTIMECMP register. This only stores 32 bits so I am not sure if that is correct... + li t3, MTIME_FREQUENCY # get clock freq (approx.) + mul t3, t3, a0 # multiply milliseconds with freq + add t4, t1, t3 # target mtime is now in t4 + li t0, MTIMECMP # load address of MTIMECMP register + sw t2, 4(t0) # set higher 32bits of MTIMECMP + sw t4, 0(t0) # store target time to MTIMECMP register. This only stores 32 bits so I am not sure if that is correct... lw ra, 12(sp) # load return address addi sp, sp, 16 # deallocate stack frame |