temp              set       60h         ;Init program constants
ram_addr       .set      61h
ram_word      .set      62h
hi_byte           .set     63h
dummyport   .set      0h

**
**  This section is loaded and executed within internal RAM block
**
     .sect     ÒBOOT_CODEÓ      ;Section compiled to run at 0xFA00

EPROM_START                        ;External EPROM starts with branch
     b         BOOT_START           ;  instruction for signature sensing

BOOT_START
     ldpk     0
     lrlk       AR0,( 8000h | APPCODE_START )
     larp      AR0                         ;EPROM start = APPCODE_START
     lalk      8000h
     sacl      ram_addr                ;External RAM start = 0x8000
     call      TRANSFER               ;Move first half of EPROM to
                                                 ;  RAM[0x8000 to almost BFFF]

     in        temp,dummyport   ;Set EPROM address bit to upper half
                                                 ;  and enable BIO- signal

     lrlk      AR0,8000h              ;Reset EPROM pointer to 0x8000

     lalk      7FFFh                      ;Set MSB of RAM address to Ò0Ó to
     and      ram_addr                ;  allow writes to external RAM and
     sacl      ram_addr                ;  not over-write internal boot
                                                 ;  loaded RAM at 0xFA00

     call      TRANSFER               ;Move second half of EPROM to
                                                 ;  alias of address
                                                 ;  RAM[almost 0xBFFF to almost FFFF]

; All code loaded from EPROM. Now jump to application code in RAM.

     b          8000h

; Subroutine ÒTRANSFERÓ converts high byte, low byte pairs
; in external EPROM to 16 bit words and stores them in external RAM

TRANSFER                               ;Ó*Ó always points to EPROM bytes
     lack      255
     and      *+
     sacl      hi_byte                    ;Mask and save high byte

     lack      255
     and      *+
     add      hi_byte,8                ;Mask low byte, combine with high
     sacl      ram_word               ;  byte and store for transfer

     zals      ram_addr
     tblw     ram_word               ;Copy word to external RAM
     addk    1
     sacl      ram_addr                ;Calc next external RAM address

     sar       AR0,temp                ;Test for EPROM address to wrap to
     lac       temp                        ;  0x0000
     bnz      TRANSFER              ;Loop until half of EPROM transferred


**
**  This section is loaded and executed within external RAM block
**  starting at address 0x8000

     .sect     ÒAPP_CODEÓ          ;Section compiled to run at 0x8000

APPCODE_START
( continue on with remaining application code ... )