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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
handle_reg:
LSRS R1, 4
MOVS R3, 0x0F
ANDS R0, R3
// R1 = 3 or 4
// R0 = shift amount
BL register
B done_stuff
handle_imm:
BL octal
B done_stuff
handle_brackets:
// expect bracket
// echo bracket
LSRS R2, 0x8
BEQ next_instr
Back
...
done_stuff:
LSRS R2, 0x4
BEQ done
MOVS R0, 0
ORRS R0, R9
BL uart_send // echo the comma (or bracket)
expect:
BL get_char
MOVS R1, ' // space char
CMP R0, R1
BNE expect // keep trying if not space
BL uart_send // echo the space
B more
done:
TST R8, R8 // R8 == whether we are in bracket or not
BEQ no_brackets
MOVS R0, ']
BL uart_send
no_bracket:
// echo carriage return + newline
B next_instr
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