last_editted_version.txt

.global asm_main
.align 4
memory: .space 2000000 ;@ 2MB reserved for own use throughout program
.align 4
Zmem: .space 2000000 ;@ 2MB for uploading Zprogram
.align 4
Zstack: .space 1000000 ;@ 1MB for Zstack
.align 4
FZreg: .space 1000000 ;@ 1MB for function local Zregisters
.align 4
temp: .space 256 ;@ 256B temporary storage for holding temp
;@ operands to variable operand count instructions
.align 4

asm_main:

;@ Set up transmitter to what TeraTerm is expecting
;@ receiver is already set up
LDR R9, =0x20

LDR R4, =0xE0001004 ;@ Mode Register -- Tera Term transmitter
STR R9, [R4, #0]

;@ Start Baud rate setup
LDR R9, =0x3E ;@ 62 in decimal value
LDR R4, =0xE0001018 ;@ Baud rate generator
STR R9, [R4, #0]

;@ Complete baud rate setup
LDR R9, =0x6
LDR R4, =0xE0001034 ;@ Baud rate divider
STR R9, [R4, #0]

;@ Enable and reset the UART
LDR R9, =0x117
LDR R4, =0xE0001000 ;@ Control register
STR R9, [R4, #0]
  LDR R7, =Zmem
  MOV R4, #0
  LDRB R8, =0b11100101
  STRB R8, [R7, R4]
  ADD R4, R4, #1
  LDRB R8, =0b11111111
  STRB R8, [R7, R4]
  ADD R4, R4, #1
  LDRB R8, =0b01000101
  STRB R8, [R7, R4]
  MOV R4, #0


decode_instructions_loop:
  LDRB R8, [R7, R4] ;@ Fetch byte from Zmem at ZPC -- Opcode
  ADD R4, R4, #1
  LSR R9, R8, #6 ;@ shift the bits we want to the right end
  CMP R9, #3 ;@ C-Type - 11
  BEQ c_type
  CMP R9, #2 ;@ A-Type - 10
  BEQ a_type
  CMP R9, #1 ;@ B-Type - 01
  BEQ b_type
  //MOV PC, LR

a_type:
  LDR R10, =48 ;@ bits 5 & 4
  AND R11, R8, R10
  CMP R11, #48 ;@ operand count is zero - 11
  CMP R11, #0 ;@ two byte constant - 00
  CMP R11, #16 ;@ one byte constant - 01
  CMP R11, #32 ;@ one byte register indicator - 10
  LDR R12, =15 ;@ instruction indicator -- bits 3 - 0
  AND R9, R8, R12

b_type:
  LDR R10, =64
  AND R11, R8, R10
  CMP R11, #0 ;@ 1st operand: one byte constant
  CMP R11, #64 ;@ 1st operand: operand in a register
  LDR R10, =32
  AND R11, R8, R10
  CMP R11, #0 ;@ 2nd operand: one byte constant
  CMP R11, #32 ;@ 2nd operand: operand in register

c_type:
  LDR R10, =31
  AND R9, R8, R10
  PUSH {R9} ;@ instruction indicator
  LDR R10, =32
  AND R9, R8, R10
  CMP R9, #0 
  BEQ two_operands ;@ two operands
  BNE var_operands ;@ variable operand count


Decode_text:
/*
Store_Opcodes:
  LDRB R0, =Zmem
  MOV R2, #0
  LDR R9, =0x0 ;@ RTRUE
  BL inc_counter
  LDR R9, =0x1 ;@ RFALSE
  BL inc_counter
  LDR R9, =0x2 ;@ PRINT
  BL inc_counter
  LDR R9, =0x3 ;@ PRINT_RET
  BL inc_counter
  LDR R9, =0x8 ;@ RET_POPPED
  BL inc_counter
  LDR R9, =0xB ;@ NEW_LINE
  BL inc_counter
  LDR R9, =0xD ;@ VERIFY
  BL inc_counter
  LDR R9, =0xE ;@ Extended opcode
  BL inc_counter
  LDR R9, =0xF ;@ PIRACY
  BL inc_counter
  LDR R9, =0xD ;@ VERIFY
  BL inc_counter
*/
inc_counter:
  STR R9, [R0, R2]
  ADD R2, R2, #1 ;@ increment Zmem offset
  ADD R9, R9, #1
  MOV R15, R14

no_operands:
OP0_0: ;@ RTRUE
OP0_1: ;@ RFALSE
OP0_2: ;@ PRINT
OP0_3: ;@ PRINT_RET
OP0_8: ;@ RET_POPPED
OP0_B: ;@ NEW_LINE
OP0_D: ;@ VERIFY
OP0_E: ;@ Extended opcode

one_operand:
OP1_00: ;@ JZ
OP1_1: ;@ GET_SIBLING
OP1_2: ;@ GET_CHILD
OP1_3: ;@ GET_PARENT
OP1_5: ;@ INC
OP1_6: ;@ DEC
OP1_8: ;@ CALL_IS
OP1_B: ;@ RET
OP1_D: ;@ PRINT_PADDR
OP1_F: ;@ CALL_IN

two_operands:
B c_type
/*
  POP {R9}

  LDR R10, =#0x00
  CMP R9, R10
  BEQ crash_mode ;@ Illegal instruction

  LDR R10, =#0x01
  CMP R9, R10
  BEQ OP2_01 ;@ JE
  LDR R10, =#0x02
  CMP R9, R10
  BEQ OP2_02 ;@ JL
  LDR R10, =#0x03
  CMP R9, R10
  BEQ OP2_03 ;@ JG

  LDR R10, =#0x04
  CMP R9, R10
  BEQ crash_mode ;@ DEC_CHK
  LDR R10, =#0x05
  CMP R9, R10
  BEQ crash_mode ;@ INC_CHK

  LDR R10, =#0x06
  CMP R9, R10
  BEQ OP2_06 ;@ JIN
  LDR R10, =#0x07
  CMP R9, R10
  BEQ OP2_07 ;@ TEST
  LDR R10, =#0x08
  CMP R9, R10
  BEQ OP2_08 ;@ JG
  LDR R10, =#0x09
  CMP R9, R10
  BEQ OP2_09 ;@ AND
  LDR R10, =#0x0A
  CMP R9, R10
  BEQ OP2_0A ;@ TEST_ATTR
  LDR R10, =#0x0B
  CMP R9, R10
  BEQ OP2_0B ;@ SET_ATTR
  LDR R10, =#0x0C
  CMP R9, R10
  BEQ OP2_0C ;@ CLEAR_ATTR
  LDR R10, =#0x0D
  CMP R9, R10
  BEQ OP2_0D ;@ STORE

  LDR R10, =#0x0E
  CMP R9, R10
  BEQ OP2_0E ;@ INSERT_OBJ
  LDR R10, =#0x0F
  CMP R9, R10
  BEQ OP2_0F ;@ LOADW
  LDR R10, =#0x10
  CMP R9, R10
  BEQ OP2_10 ;@ LOADB
  LDR R10, =#0x11
  CMP R9, R10
  BEQ OP2_11 ;@ GET_PROP

  LDR R10, =#0x14
  CMP R9, R10
  BEQ OP2_14 ;@ ADD
  LDR R10, =#0x15
  CMP R9, R10
  BEQ OP2_15 ;@ SUB
  LDR R10, =#0x16
  CMP R9, R10
  BEQ OP2_16 ;@ MUL
  LDR R10, =#0x17
  CMP R9, R10
  BEQ OP2_17 ;@ DIV
  LDR R10, =#0x18
  CMP R9, R10
  BEQ OP2_18 ;@ MOD
  LDR R10, =#0x19
  CMP R9, R10
  BEQ OP2_19 ;@ CALL_2S
  LDR R10, =#0x1A
  CMP R9, R10
  BEQ OP2_1A ;@ CALL_2N
  LDR R10, =#0x1B
  CMP R9, R10
  BEQ OP2_1B ;@ SET_COLOUR

  LDR R10, =#0x1C
  CMP R9, R10
  BEQ crash_mode ;@ crash_mode
  LDR R10, =#0x1D
  CMP R9, R10
  BEQ crash_mode ;@ crash_mode
  LDR R10, =#0x1E
  CMP R9, R10
  BEQ OP2_1E ;@ crash_mode
  LDR R10, =#0x1F
  CMP R9, R10
  BEQ crash_mode ;@ crash_mode


OP2_01: ;@ JE
OP2_02: ;@ JL
OP2_03: ;@ JG
OP2_06: ;@ JIN
OP2_08: ;@ OR
OP2_09: ;@ AND
OP2_0A: ;@ TEST_ATTR
OP2_0B: ;@ SET_ATTR
OP2_0C: ;@ CLEAR_ATTR
OP2_0D: ;@ STORE
OP2_14: ;@ ADD
  ADD R4, R4, #1
  LDR R8, [R7, R4]
  MOV R10, #6
  PUSH {R8-R12}
  BL fetch_next
  POP {R8-R12}
*/

var_operands:
  POP {R9}
  CMP R9, #5
  BEQ VAR_05 ;@ PRINT_CHAR
  BNE var_operands

  ;@BNE carsh
VAR_05: ;@ PRINT_CHAR
  ADD R4, R4, #1
  BL Fetch_OP ;@ USING BL HERE MAY HAVE TO NEST IT
  LDR R8, [R7, R4]
  LDR R12, =0xE0001030
  STR R8, [R12,#0]
  B done

Fetch_OP:
  LDR R12, =0b11000000
  LDR R8, [R7, R4]
  LDR R11, =memory
  STR R8, [R11, #100] ;@storing the operand decoder in #100th space in memory
  loop:
  LDR R8, [R11, #100]
  ADD R11, R8, R12
  CMP R11, #0
  BEQ 16_bit_constant
  CMP R11, #1
  BEQ 8_bit_constant
  CMP R11, #2
  BEQ operand_in_register
  CMP R11, #3
  MOVEQ PC,LR ;@ RETURNING TO BL HERE MAY HAVE TO NEST IT
  LSR R12, #2
  B loop

16_bit_constant:
  LDR R11, =memory
  ADD R4, R4, #1
  LDRH R0, [R7, R4] 
  STRH R0, [R11, #104]
  ADD R4, R4, #2
  
  B loop
  
  done:
  B done