68 lines
1.6 KiB
NASM
68 lines
1.6 KiB
NASM
sendBufferAsm:
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push {r4,r5,r6,r7,lr}
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mov r4, r0 ; save buff
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mov r6, r1 ; save pin
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mov r0, r4
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bl BufferMethods::length
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mov r5, r0
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mov r0, r4
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bl BufferMethods::getBytes
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mov r4, r0
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; setup pin as digital
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mov r0, r6
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movs r1, #0
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bl pins::digitalWritePin
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; load pin address
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mov r0, r6
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bl pins::getPinAddress
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ldr r0, [r0, #8] ; get mbed DigitalOut from MicroBitPin
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ldr r1, [r0, #4] ; r1-mask for this pin
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ldr r2, [r0, #16] ; r2-clraddr
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ldr r3, [r0, #12] ; r3-setaddr
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cpsid i ; disable irq
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b .start
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.nextbit: ; C0
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str r1, [r3, #0] ; pin := hi C2
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tst r6, r0 ; C3
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bne .islate ; C4
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str r1, [r2, #0] ; pin := lo C6
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.islate:
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lsrs r6, r6, #1 ; r6 >>= 1 C7
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bne .justbit ; C8
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; not just a bit - need new byte
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adds r4, #1 ; r4++ C9
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subs r5, #1 ; r5-- C10
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bcc .stop ; if (r5<0) goto .stop C11
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.start:
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movs r6, #0x80 ; reset mask C12
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nop ; C13
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.common: ; C13
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str r1, [r2, #0] ; pin := lo C15
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; always re-load byte - it just fits with the cycles better this way
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ldrb r0, [r4, #0] ; r0 := *r4 C17
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b .nextbit ; C20
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.justbit: ; C10
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; no nops, branch taken is already 3 cycles
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b .common ; C13
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.stop:
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str r1, [r2, #0] ; pin := lo
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cpsie i ; enable irq
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pop {r4,r5,r6,r7,pc}
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