8051アセンブリプログラミングでの命令サイズの計算方法（ADD A、Rn - > 1byte ..？）私は、アセンブリプログラミングに新たなんだ

Question

、

ADD A,Rn 

は1バイト命令と

ADD A,direct 

は2バイト命令でした。どうして？

Answer 1

ADD A,Rnは、オペコード+レジスタ番号を1バイトでエンコードできるため、1バイト命令です。サイズ> 1を説明したパラメータを、（保持する

base_operand = 0x28 (only 6 bits are required) 
R_register_index = 0->7 (only 3 bits are required) 

instruction = base operand OR R_register_index 

ADD A,R0 0x28 
ADD A,R1 0x29 
ADD A,R2 0x2A 
ADD A,R3 0x2B 
ADD A,R4 0x2C 
ADD A,R5 0x2D 
ADD A,R6 0x2E 
ADD A,R7 0x2F 

ADD A,directニーズ1オペコードのためのバイトと少なくとも別のバイト：

で構成されている1バイトに保持する8つの異なるオペコードがあります。例：MOV RO,#12H：2バイト）

命令サイズの範囲は1〜3バイトですが、命令のサイズについて絶対的なルールはありません。 （2つのパラメータを持ついくつかの命令については、メモリから読み込みます）

参照hereを確認して、すべての指示をメモリに保存してください。&

サイズを計算する信頼性の高い方法は、命令サイズテーブル（IST）を作成することです：opcode => size。

これは、デバッガが次の命令アドレスを「予測」する方法です。完全を期すために

、私はあなたにこのテーブルを提供してみましょう（ $A5を保有し、命令ではありませんのでご注意：私はサイズを0に設定）

op  sz 
$00 => 1 
$01 => 2 
$02 => 3 
$03 => 1 
$04 => 1 
$05 => 2 
$06 => 1 
$07 => 1 
$08 => 1 
$09 => 1 
$0A => 1 
$0B => 1 
$0C => 1 
$0D => 1 
$0E => 1 
$0F => 1 
$10 => 3 
$11 => 2 
$12 => 3 
$13 => 1 
$14 => 1 
$15 => 2 
$16 => 1 
$17 => 1 
$18 => 1 
$19 => 1 
$1A => 1 
$1B => 1 
$1C => 1 
$1D => 1 
$1E => 1 
$1F => 1 
$20 => 3 
$21 => 2 
$22 => 1 
$23 => 1 
$24 => 2 
$25 => 2 
$26 => 1 
$27 => 1 
$28 => 1 
$29 => 1 
$2A => 1 
$2B => 1 
$2C => 1 
$2D => 1 
$2E => 1 
$2F => 1 
$30 => 3 
$31 => 2 
$32 => 1 
$33 => 1 
$34 => 2 
$35 => 2 
$36 => 1 
$37 => 1 
$38 => 1 
$39 => 1 
$3A => 1 
$3B => 1 
$3C => 1 
$3D => 1 
$3E => 1 
$3F => 1 
$40 => 2 
$41 => 2 
$42 => 2 
$43 => 3 
$44 => 2 
$45 => 2 
$46 => 1 
$47 => 1 
$48 => 1 
$49 => 1 
$4A => 1 
$4B => 1 
$4C => 1 
$4D => 1 
$4E => 1 
$4F => 1 
$50 => 2 
$51 => 2 
$52 => 2 
$53 => 3 
$54 => 2 
$55 => 2 
$56 => 1 
$57 => 1 
$58 => 1 
$59 => 1 
$5A => 1 
$5B => 1 
$5C => 1 
$5D => 1 
$5E => 1 
$5F => 1 
$60 => 2 
$61 => 2 
$62 => 2 
$63 => 3 
$64 => 2 
$65 => 2 
$66 => 1 
$67 => 1 
$68 => 1 
$69 => 1 
$6A => 1 
$6B => 1 
$6C => 1 
$6D => 1 
$6E => 1 
$6F => 1 
$70 => 2 
$71 => 2 
$72 => 2 
$73 => 1 
$74 => 2 
$75 => 3 
$76 => 2 
$77 => 2 
$78 => 2 
$79 => 2 
$7A => 2 
$7B => 2 
$7C => 2 
$7D => 2 
$7E => 2 
$7F => 2 
$80 => 2 
$81 => 2 
$82 => 2 
$83 => 1 
$84 => 1 
$85 => 3 
$86 => 2 
$87 => 2 
$88 => 2 
$89 => 2 
$8A => 2 
$8B => 2 
$8C => 2 
$8D => 2 
$8E => 2 
$8F => 2 
$90 => 3 
$91 => 2 
$92 => 2 
$93 => 1 
$94 => 2 
$95 => 2 
$96 => 1 
$97 => 1 
$98 => 1 
$99 => 1 
$9A => 1 
$9B => 1 
$9C => 1 
$9D => 1 
$9E => 1 
$9F => 1 
$A0 => 2 
$A1 => 2 
$A2 => 2 
$A3 => 1 
$A4 => 1 
$A5 => 0 
$A6 => 2 
$A7 => 2 
$A8 => 2 
$A9 => 2 
$AA => 2 
$AB => 2 
$AC => 2 
$AD => 2 
$AE => 2 
$AF => 2 
$B0 => 2 
$B1 => 2 
$B2 => 2 
$B3 => 1 
$B4 => 3 
$B5 => 3 
$B6 => 3 
$B7 => 3 
$B8 => 3 
$B9 => 3 
$BA => 3 
$BB => 3 
$BC => 3 
$BD => 3 
$BE => 3 
$BF => 3 
$C0 => 2 
$C1 => 2 
$C2 => 2 
$C3 => 1 
$C4 => 1 
$C5 => 2 
$C6 => 1 
$C7 => 1 
$C8 => 1 
$C9 => 1 
$CA => 1 
$CB => 1 
$CC => 1 
$CD => 1 
$CE => 1 
$CF => 1 
$D0 => 2 
$D1 => 2 
$D2 => 2 
$D3 => 1 
$D4 => 1 
$D5 => 3 
$D6 => 1 
$D7 => 1 
$D8 => 2 
$D9 => 2 
$DA => 2 
$DB => 2 
$DC => 2 
$DD => 2 
$DE => 2 
$DF => 2 
$E0 => 1 
$E1 => 2 
$E2 => 1 
$E3 => 1 
$E4 => 1 
$E5 => 2 
$E6 => 1 
$E7 => 1 
$E8 => 1 
$E9 => 1 
$EA => 1 
$EB => 1 
$EC => 1 
$ED => 1 
$EE => 1 
$EF => 1 
$F0 => 1 
$F1 => 2 
$F2 => 1 
$F3 => 1 
$F4 => 1 
$F5 => 2 
$F6 => 1 
$F7 => 1 
$F8 => 1 
$F9 => 1 
$FA => 1 
$FB => 1 
$FC => 1 
$FD => 1 
$FE => 1 
$FF => 1