; slotData.asm
; A boot slot payload that arranges its own Data Segment.
;
; Stage one places Program Memory and nothing else, because knowing where a payload's data
; ends and its code begins would mean knowing a format, and knowing formats is the thing
; ROM must do as little of as possible. So a payload that wants initialised data arranges
; it: a loadable image is written into the slot as code followed by data, which leaves the
; data image sitting in Program Memory just past the code, and the first thing the payload
; does is blit it down to where it was assembled for.
;
; This is how the real second stage will get the Data Segment that sbfs.asm needs.
;
; THE PADDING IS NOT DECORATION. The blit needs a length, the assembler will not work out
; a difference between two labels, so the segment is padded to a round number and that
; number is what gets copied. Reserve one byte too many and the last byte does not arrive:
; the first draft of this padded to 257 and copied 256.
;
; Written by Anachronaut
#Program
  #Base 0xC000

start:
  RSTA
  OUTA 0xE0             ; SourceBank: Program Memory, where stage one put everything.
  SETD.0 codeEnd
  PSHD.0
  POPA
  POPB
  OUTB 0xE1
  OUTA 0xE2
  INIA 0d1
  OUTA 0xE3             ; DestBank: Data Memory.
  SETD.0 Greeting
  PSHD.0
  POPA
  POPB
  OUTB 0xE4
  OUTA 0xE5
  INIA 0x01
  OUTA 0xE6
  RSTA
  OUTA 0xE7             ; A round 256 bytes, which the segment is padded to.
  INIA 0x01
  OUTA 0xE8

  SETD.0 Greeting
sayLoop:
  LDA.0
  BRA sayDone
  OUTA 0x00
  INCD.0
  BRI sayLoop
sayDone:
  HALT

codeEnd:

#Data
  #Base 0x3000

Greeting:
"a payload with data of its own
"
Padding:
  #Reserve 0d224