97 lines
2.9 KiB
Markdown
97 lines
2.9 KiB
Markdown
# Cardiograph-I — simulator for a paper computer
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## Dependencies
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Node.js
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## Run
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### Assemble
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Hex output:
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```./run-assembler run source_code.asm```
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Binary output:
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```./run-assembler runbin source_code.asm```
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Verbose debugging output (hex):
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```./run-assembler debug source_code.asm```
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### Assemble and run
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With animated display of screen memory:
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```./run-cpu run source_code.asm```
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With verbose debugging output:
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```./run-cpu debug source_code.asm```
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## Instruction set
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00 END
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01 STO lit# ; store ... mem[lit#] <- A
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02 STO addr ; store ... mem[mem[addr]] <- A
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03 LDA lit# ; load ... A <- lit#
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04 LDA addr ; load ... A <- mem[addr]
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05 ADD lit# ; add ... A <- A + lit# ... and un/set carry flag
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06 ADD addr ; add ... A <- A + mem[addr] ... and un/set carry flag
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07 SUB lit# ; sub ... A <- A - lit# ... and un/set carry flag
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08 SUB addr ; sub ... A <- A - mem[addr] ... and un/set carry flag
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09 HOP lit# ; hop ... skip next instruction if A == lit# ... when true: IP <- PC + 4
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0A HOP addr ; hop ... skip next instruction if A == addr ... when true: IP <- PC + 4
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0B JMP lit# ; jump ... IP <- lit#
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0C JMP addr ; jump ... IP <- addr
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0D FTG lit# ; toggle flag by number (see details below)
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0E FHP lit# ; flag hop ... skip next instruction if flag is set ... when true: IP <- PC + 4
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0F NOP ———— ; no operation
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- Instructions are two bytes long:
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one byte for the opcode, one for the operand
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## Registers and Flags
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- `A` - accumulator
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- `IP` - instruction pointer (aka program counter)
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- `FLAGS` - flags: **N**egative, **Z**ero, **O**verflow, **C**arry
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- in machine language, each flag is given a number:
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- N = 3
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Z = 2
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O = 1
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C = 0
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- (bitwise, `0000 = NZOC`)
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## Memory map / Peripherals
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- `00-19` - display (5x5)
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- `20 ` - keypad (details TBD)
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- `21 ` - pointer to display memory
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- `22 ` - pointer to keypad memory
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- `23-2F` - reserved for future use / variable storage
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- `30 ` - initial value for IP
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- `30-FF` - free
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## Assembly language
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ADD $01 ; comments follow a `;`
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ADD $FF ; this is direct addressing
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ADD ($CC) ; this is indirect addressing
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END ; END and NOP don't require operands
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; (the assembler will fill in a default value of 0)
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@subroutine ; create a label
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ADD $01 ; (it must be on the line before the code it names)
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ADD $02
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JMP @subroutine ; use a label as operand
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; the label will be replaced with
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; the address of the label
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=foo $FF ; define a constant
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; (must be defined before it is referenced)
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ADD =foo ; use a constant as an operand
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- Hexadecimal numbers are preceded by a `$`
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- Whitespace is ignored |