The wAx API

The following subroutines will be useful in the development of user plug-ins.

##Routine Addr2CP

Copy Working Address to Command Pointer

Call Address: $A027

Affected Registers: Accumulator

Description: Copies the Working Address, which is usually the current address for a wAx process, to the Command Pointer, which indicates the next default address.

##Routine: Buff2Byte

Get hexadecimal byte from input

Call Address: $A003

Affected Registers: Accumulator, X

Description: If the next two non-space characters in the input buffer represent a valid hexadecimal byte, the value is returned in the Accumulator and the Carry flag is set. Otherwise, the carry flag is clear.

##Routine: CharGet

Get character from input

Call Address: $A006

Affected Registers: Accumulator, X Description: Gets the next character from the input buffer. Spaces are not returned unless within quotes. Accumulator of 0 indicates end of input.

##Routine: CharOut

Add character to output

Call Address: $A009

Affected Registers: None

Description: Adds a character with PETSCII code in Accumulator to the output buffer. Note that the output buffer is not flushed to the screen until PrintBuff is called.

##Routine: Hex

Add hexadecimal byte to the output buffer

Call Address: $A00C

Affected Registers: Accumulator, X

Description: Adds the value in the accumulator to the output buffer as a two-character hexadecimal number. Note that the output buffer is not flushed to the screen until PrintBuff is called.

##Routine: IncAddr

Increment the working address

Call Address: $A00F

Affected Registers: Accumulator, X

Description: Sets Accumulator to the value of the working address, then increment the working address. The Accumulator will be the value of the address prior to the increment.

##Routine: IncCP

Increment the Command Pointer

Call Address: $A012

Affected Registers: None

Description: Increments the Command Pointer.

##Routine: Install

Start wAx

Call Address: $A000

Affected Registers: Accumulator, X, Y

Description: This is the jump to starting wAx with SYS 40960.

##Routine: Lookup

Get 6502 instruction data

Call Address: $A015

Affected Registers: Accumulator, X, Y

Description: Looks up a 6502 instruction with the opcode in the Accumulator. The Carry flag is set if it's a valid instruction. The instruction's addressing mode is returned in the Accumulator. The instruction's mnemonic is packed in zeropage locations $A4 and $A5, with five bits per letter in bits 0-14.

You may include "illegal" opcodes in the lookup by setting zeropage location $AF to value $2C in preparation for the call.

##Routine: PrintBuff

Flush output buffer to screen

Call Address: $A018

Affected Registers: Accumulator, Y

Description: Flushes the output buffer to the screen or output device, to a limit of 22 characters. The output buffer is terminated by $00. PrintBuff always ends with Reverse Off and Linefeed. Note that PrintBuff does not reset the buffer itself, so a new line should be started with ResetOut.

##Routine: ResetIn

jLookup: jmp Lookup ; a015 jPrintBuff: jmp PrintBuff ; a018 jResetIn: jmp ResetIn ; a01b jResetOut: jmp ResetOut ; a01e jShowAddr: jmp ShowAddr ; a021 jShowCP: jmp ShowCP ; a024 jEAtoCP: jmp EAtoCP ; a027 jPrintStr: jmp PrintStr ; a02a jNextList: jmp NextList ; a02d jDirectMode:jmp DirectMode ; a030 jSizeOf: jmp SizeOf ; a033