kip/d/kmx20.md

title: kip manual: kmx20 ... # kmx20 cpu This document is heavily incomplete. It is a work-in-progress effort. ## Hardware registers The kmx20 has 3 hardware registers, - ip Word Instruction pointer - dp Byte Data Stack Pointer - rp Byte Return Stack Pointer ## Busses The kmx20 has 2 data busses. - mem - Memory bus - Byte-addressed - Where data is to be read and writ +---0x00000---+ <-- Interrupt Vector Table | (rwx) | +---0x00100---+ <-- Boot | (rwx) | This is where the CPU resets to, | | and where the emulator puts | | loaded ROMs. . . . . . . | | +---0x40000---+ <-- Data Stack | (rw-) | Word-addressed by `dp +---0x40400---+ <-- Return Stack | (rw-) | Word-addressed by `rp +---0x40800---+ - io - Input/Output Bus - Word-addressed - Peripherals are directly connected to this bus - See kip.md for kip computer i/o ## Instructions Instructions take 1 byte in memory. Each binary digit corresponds to XFOOOOOO |||O: Opcode ||F: Flip return and data stacks || (eg 01000010 will put the next byte in memory onto the return stack) |K: Keep left hand operands | (eg (a--n) below becomes (a--a n)) |X: Unused ## Opcodes | Op | Stack effect | Description | |----|--------------|-----------------------------------------------------------------------------| |np|-- | no-op | |ex|-- | halt execution | |pb|--n | puts the next byte (8 bits) in memory onto the stack | |ph|--n | ^ same but next half-word (16 bits) | |pw|--n | ^ same but next word (32 bits) | |pr|--n | puts ip+the next byte plus onto the stack | |fb|a--n | fetches a byte from address `a and puts it onto the stack | |fh|a--n | ^ same but with half-word | |fw|a--n | ^ same but with word | |mb|n a-- | truncate stack item `n into a byte and put it in memory address `a | |mh|n a-- | ^ same but with half-word | |mw|n a-- | ^ same but with word | |io|n p-- | move cell `n to io port `p | |ii|p--n | gets cell from io port `p and pushes it onto the stack | |ss|n-~n | move cell from data stack to return stack | |dr|n-- | drop item from data stack | |sw|n m--m n | swap items | |du|n--n n | duplicate item on data stack | |ov|n m--n m n | bring second item on data stack over | |ad|n m--n+m | add | |su|n m--n-m | subtract | |mu|n m--n*m | multiply | |di|n m--n/m n%m| div rem | |an|n m--n&m | bitwise and | |or|n m--n|m | bitwise or | |xr|n m--n^m | bitwise xor | |sl|n m--n<<m | bitwise shift left | |sr|n m--n>>m | bitwise shift right | |sa|n m--n>>>m | bitwise arithmetic shift right | |eq|n m--n==m | logical equals | |lt|n m--n<m | logical less than | |gt|n m--n>m | logical greater than | |no|n--!n | logical not | |ju|a-- | jump to address a | |jc|n a-- | jump to addressa if n!=0 | |ca|a-~r | push ip onto return stack, then jump to addressa | |cc|n a-~r | push ip onto return stack and jump to address a if n!=0 |