Improve assembler sketch

1 files changed, 55 insertions, 61 deletions

diff --git a/assembler/assemble.s b/assembler/assemble.s
index 96940ea..bf31edf 100644
--- a/assembler/assemble.s
+++ b/assembler/assemble.s
@@ -1,77 +1,71 @@
-1yyyxxxx Imm         yyy = shift amount xxxx = bit-width
-00000001 Brackets
-0011yyyy Reg        yyyy = shift amount
-0100yyyy Reg
-
-MOVS 0x 00 00 88 38
-ADDS 0x 00 00 88 38
-SUBS 0x 00 00 88 38
-CMP  0x 00 00 33 30
-ANDS 0x 00 00 33 30
-ORRS 0x 00 00 33 30
-TST  0x 00 00 33 30
-LSLS 0x 00 E5 33 30
-LSRS 0x 00 E5 33 30
-RORS 0x 00 00 33 30
-LDR  0x E5 33 01 30
-LDRB 0x 36 33 01 30
-STR  0x E5 33 01 30
-STRB 0x 36 33 01 30
-B<c> 0x 00 00 00 88
-B    0x 00 00 00 8B
-BX   0x 00 00 00 43
-
-// R2 holds the whole word
-// R0 holds just the byte
-// R1 holds either 3 or 4
-more:
-  MOVS R0, 0xFF
-  ANDS R0, R2
-  MOVS R1, 0x80
-  TST R0, R1
-  BNE handle_imm // if IMM
-  MOVS R1, 0xF0
-  ANDS R1, R0
-  BEQ handle_brackets // if BRACKETS
+assemble:
+  BL receive_op
+  LDR R5, =0x20002000 // opcode table
+  LDR R1, =0x20001000 // opcode buffer base addr
+loop:
+  LDR R0, [R5, 0]     // load the string addr
+  BL string_compare
+  BEQ match
+  ADDS R5, 8          // next row of table
+  LDR R0, =0x20002080 // opcode table end
+  CMP R5, R0
+  BLO loop            // Keep going if lower than end
+  B redo_line         // redo line if opcode was not found
+match:
+  LDR R6, [R5, 4]     // load the parse instructions
+main_loop:
+  MOVS R0, 0xFF   // lsb mask
+  ANDS R0, R6     // store in R0
+  MOVS R1, 0x80   // bit 7 mask
+  TST R0, R1      // compare (AND) to R0 byte
+  BNE handle_imm  // if IMM (== 1)
+  LSRS R0, 4      // R0 hold 3 or 4 (or 0)
+  BEQ handle_brackets // if BRACKETS (== 0)
 handle_reg:
-  LSRS R1, 4
-  MOVS R3, 0x0F
-  ANDS R0, R3
-  // R1 = 3 or 4
-  // R0 = shift amount
-  BL register
+  BL register    // result is put in R4
+  MOVS R0, 0x0F  // lower nibble mask
+  ANDS R0, R6    // store shift amount in R0
+  LSLS R4, R0    // shift the result by the shift amount
+  ORRS R5, R4    // OR the register code into the word under construction
   B done_stuff
-
 handle_imm:
-  BL octal
-  B done_stuff
-
-handle_brackets:
-  // expect bracket
-  // echo bracket
-  LSRS R2, 0x8
-  BEQ next_instr
-  Back
-  ...
-
+  MOVS R1, 0x0F  // lower nibble mask
+  ANDS R0, R1    // store immediate width in R0
+  BL octal       // result is put in R4
+  MOVS R0, 0x7F  // least significant 7 bits mask
+  ANDS R0, R6    // store ls 7 bits in R0
+  LSRS R0, 4     // shift right to get shift amount
+  LSLS R4, R0    // shift the result by the shift amount
 done_stuff:
-  LSRS R2, 0x4
-  BEQ done
-  MOVS R0, 0
+  LSRS R6, 0x8 // get next parse instruction
+  BEQ done     // if it's zero there are no more things to parse
+  MOVS R0, 0   // copy the end_char into R0
   ORRS R0, R9
   BL uart_send // echo the comma (or bracket)
-expect:
+10:
   BL get_char
   MOVS R1, '  // space char
   CMP R0, R1
-  BNE expect // keep trying if not space
+  BNE 10b // keep trying if not space
   BL uart_send // echo the space
-  B more
+  B main_loop
+handle_brackets:
+  BL get_char    // char in R0
+  MOVS R1, '[    // open bracket
+  CMP R0, R1
+  BNE handle_brackets // keep trying if not bracket
+  BL uart_send   // echo bracket
+  MOVS R8, 1     // 1 means we are now in brackets
+  LSRS R6, 0x8   // get next parse instruction
+  BNE main_loop
 done:
   TST R8, R8 // R8 == whether we are in bracket or not
   BEQ no_brackets
-  MOVS R0, ']
+  MOVS R0, ']  // echo bracket
   BL uart_send
 no_bracket:
-  // echo carriage return + newline
+  MOVS R0, '\r  // send carriage return
+  BL uart_send
+  MOVS R0, '\n  // send newline
+  BL uart_send
   B next_instr