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Basic Instructions Assembly Syntax Operation
--------------------- -------------------- -----------------------------
iiii iiii aaaa 0000 mov Ra, si8 Ra = si8
iiii iiii aaaa 0001 mhi Ra, si8 Ra = (Ra & 0xFF) | (si8 << 8)
ffff bbbb aaaa 0010 alu Ra, Ra, Rb Ra = Ra <fn> Rb
iiii ffff aaaa 0011 alu Ra, Ra, si4 Ra = Ra <fn> si4
ffff bbbb aaaa 01cc alu Rc, Ra, Rb Rc = Ra <fn> Rb
iiii bbbb aaaa 1000 lw Ra, [Rb, si4] Ra = [Rb + si4]
iiii bbbb aaaa 1001 sw Ra, [Rb, si4] [Rb + si4] = Ra
iiii iiii aaaa 1010 bnz Ra, si8 if (Ra != 0) PC += si8
iiii iiii aaaa 1011 bz Ra, si8 if (Ra == 0) PC += si8
iiii iiii iiii 1100 b si12 PC += si12
iiii iiii iiii 1101 bl si12 R14 = PC, PC += si12,
0000 bbbb xxxx 1110 b Rb PC = Rb
0001 bbbb xxxx 1110 bl Rb R14 = PC, PC = Rb
0010 0000 0000 1110 nop
0010 nnnn aaaa 1110 debug Ra, x4 DEBUG(Ra, n4)
Extended Instructions <--- Not implemented yet.
--------------------- Will likely change during
0011 xxxx xxxx 1110 iret implementation.
0100 nnnn aaaa 1110 mov Ra, Sn
0101 nnnn aaaa 1110 mov Sn, Ra
0110 aaaa bbbb 1110 mov Ra', Rb
0111 aaaa bbbb 1110 mov Ra, Rb'
1xxx xxxx xxxx 1110 undefined
nnnn nnnn 0000 1111 syscall n
nnnn nnnn 0001 1111 break;
nnnn nnnn 0010 1111 set <flags>
nnnn nnnn 0011 1111 clr <flags>
xxxx xxxx 0011 1111 undefined
xxxx xxxx 01xx 1111 undefined
xxxx xxxx 1xxx 1111 undefined
ALU Functions (<fn>) Key
-------------------------------------- ----------------------------------
0000 mov r = b si4 signed 4bit immediate
0001 and r = a & b si8 signed 8bit immediate
0010 orr r = a | b si12 signed 12bit immediate
0011 xor r = a ^ b fn ALU function
0100 add r = a + b R0-R15 general purpose registers
0101 sub r = a - b PC program counter
0110 mul r = a * b
0111 mhi r = (b << 8) | (a & 0xFF) S0-S15 system control registers
1000 slt r = a < b F0-F7 system flag bits
1001 sle r = a <= b R0'-R15' banked registers
1010 shr r = a >> 1
1011 shl r = a << 1
1100 bis r = a | (1 << b[3:0])
1101 bic r = a & (~(1 << b[3:0]))
1110 tbs r = a & (1 << b[3:0])
1111 bit r = 1 << b[3:0]
Register Usage / Procedure Call Standard
-----------------------------------------
R0 - R3 parameters & results
R4 - R11 caller save, working variables
R12 reserved for OS/runtime global use
R13 stack pointer
R14 link register* (for branch-and-link)
R15 scratch (for assembler/linker use)
* The processor can *only* save PC to R14 on BL calls.
All other register assignements are merely to simplify
software interworking, not required by the architecture.
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