putchar
# Description:
#   Writes one character to the terminal.
# Stack Requirements:
#   Character to write
#   Return PC <-- TOS
    WORD_134217728      # XBUF
    WORD_134217732      # XCSR
    LDSP+3
    SWAP
putcharloop
    LDSP+0
    LOAD
    TEST
    BRZ>putcharloop
    TEST # Drop XCSR from stack
    SWAP
    STORE
    # Wrote the character. Clean up stack and return.
    STSP+0
    RTS

getchar
# Description:
#   Reads one character from the terminal.
# Stack Requirements:
#   Return PC <-- TOS
    WORD_134217736      # RBUF
    WORD_134217740      # RCSR
getcharloop
    LDSP+0
    LOAD
    TEST
    BRZ>getcharloop
    LDSP+1
    LOAD
    # Found a character. Clean up stack and return.
    STSP+0
    STSP+0
    SWAP
    RTS