54 lines
2.0 KiB
Markdown
54 lines
2.0 KiB
Markdown
# zybino: LR35902ish racket language
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very early days for now.
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in the racket repl (comments for reader comprehension, remove before running):
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```
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(run-vm #x150 #x150 #x19 ; start-address, end-memory-view-addr, number-bytes-view
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'(#x3E #x69 ; LD A, $69
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#x26 #x01 ; LD H, $01
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#x2E #x67 ; LD L, $67
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#x77 ; LD (HL), A
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#x2E #x5B ; LD L, $5B
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#x36 #xE6 ; LD (HL), $E6 ($E6 is the opcode for XOR $xx)
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#x10 ; STOP (this instruction @ address $015B)
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#xF0 ; (non-instruction, will be arg for previous byte)
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#x2E #x68 ; LD L, $68
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#x77 ; LD (HL), A
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#xC2 #x64 #x01 ; JP NZ, $0164
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#x10 ; STOP
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#x7D ; LD A, L (address $0164)
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#x10 ; STOP
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))
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```
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will evaluate to:
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```
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PC: $0166, SP: $0000, Flags: %00000000
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BC: $0000, DE: $0000
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HL: $0168, AF: $6800
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(HL): $60
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$0150 > $3e $69 $26 $01 $2e $67 $77 $2e $5b $36 $e6 $e6 $f0 $2e $68 $77 $c3 $64 $01 $10 $7d $10 $00 $69 $60 < $0168
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```
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here we can see the program loaded starting from address `$0150`, including the `XOR` instruction loaded to `$015B` during execution, and the `$69` we loaded to memory, along with the result of `XOR $F0` we loaded to memory, at `$0167` and `$0168` respectively. we can also see that the `A` register is `$68`, the same as the `L` register, as the conditional `JP NZ` instruction executed properly and we skipped the `STOP` at address `$0163`.
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## notes
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currently supported instructions are:
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* `JP #addr`
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* `JP [cc], #addr`
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* `LD [reg], #imm`
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* `LD [reg], [reg]`
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* `XOR #imm`
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* `AND #imm`
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* `OR #imm`
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* `STOP`
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* `NOP`
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all other instructions treated as `NOP`
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on a gameboy, the instruction `LD (HL), (HL)` is treated as a `HALT`, however i am not making a gameboy perfect vm as of now, so opcode `$76` is currently treated as `LD (HL), (HL)`
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