Apakah Set Arahan Koleksi arahan yg lengkap yg

Apakah Set Arahan? • Koleksi arahan yg lengkap yg difahami oleh CPU • Kod Mesin (Machine code) • Perduaan (Binary) • Selalunya diwakili oleh kod 2 penghimpunan (assembly codes)

Element 2 Arahan • Kod operasi (Operation code - op code). – Buat ini (Do this). • Sumber rujukan operan (Source operand reference). – Ke ini (To this). • Rujukan jawapan operan (Result operand reference). – Letak jawapan di sini. • Rujukan arahan berikut (Next instruction reference). – Pabila ia selesai, buat ini pulak. . .

Pewakilan Arahan • Dlm kod mesin, setiap arahan mempunyai pola bit yg unik • Utk kemudahan manusia (yakni pengaturcara), pewakilan simbolik digunakan – Cth. Add, sub, load • Operan juga boleh diwakili dgn cara ini – Add a, b

Format 2 Arahan • • Paparan bit 2 dlm arahan Termasuk opcode Termasuk (tersirat atau nyata) operan 2 Selalunya lbh drpd satu format arahan dlm set arahan.

Format Arahan 4 Op-Code 6 Operand Reference 1 6 Operand Reference 2 Operand field 16 bits

Jenis 2 Arahan • • Pemprosesan data (Data processing) Penyimpanan data (Data storage - memori utama) Pergerakkan data (Data movement- I/O) Program flow control

Panjang Arahan • Dipengaruhi oleh dan mempengaruhi: – Saiz Memori – Oraganisasi Memori – Struktur bas – Kekompleksan CPU – Kelajuan CPU • Keseimbangan ant ‘powerful instruction repertoire’ & ‘saving space’.

Number of Addresses (a) • 3 addresses – Operand 1, Operand 2, Result – a = b + c; – May be a forth - next instruction (usually implicit) – Not common – Needs very long words to hold everything

Number of Addresses (b) • 2 addresses – One address doubles as operand result –a=a+b – Reduces length of instruction – Requires some extra work • Temporary storage to hold some results

Number of Addresses (c) • 1 address – Implicit second address – Usually a register (accumulator) – Common on early machines

Number of Addresses (d) • 0 (zero) addresses – All addresses implicit – Uses a stack – e. g. push a – push b – add – pop c –c=a+b

Bilangan Alamat • Mesin satu alamat – Add b => ac = ac + b • Mesin dua alamat – Sub a, b => a = a - b • Mesin tiga alamat – Add a, b, c => a = b + c

Bilangan Alamat • Arahan tiga alamat – Arahan – Sub y, a, b – MPY t, d, e – Add t, t, c – Div y, y, t komen/makna y<= a-b t<= d*e t<= t+c y<= y/t » Y= (a-b) / (c+d*e)

Bilangan Alamat • Arahan dua alamat – MOV y, a – Sub y, b – MOV t, d – MPY t, e – Add t, c – Div y, t y<= a y<= y-b t<= d t<= t*e t<= t+c y<= y/t » Y= (a-b) / (c+d*e)

Bilangan Alamat • Arahan satu alamat – – – – LOD d MPY e Add c STR y LOD a Sub b Div y STR y ac<= d ac<= ac*e ac<=ac+c y<= ac ac<= ac-b ac<= ac/y y<= ac » Y= (a-b) / (c+d*e)

Berapa banyak alamat? • Lebih alamat – Lbh komplek (powerful? ) arahan – Lbh daftar (register) • Inter-register operations are quicker – Sedikit arahan per program • Sedikit alamat – Krg komplek (powerful? ) arahan – Lbh arahan per program – Cepat Ambil/Laksana arahan

Keputusan Rekabentuk (1) • Himpunan operasi – Berapa byk operasi? – Apa yg blh dilakukan? – Berapa komplek? • Jenis 2 data • Format 2 arahan – Panjang kod operasi – Bilangan alamat

Keputusan Rekabentuk (2) • Daftar 2 (Registers) – Bil. daftar 2 CPU yg ada – Which operations can be performed on which registers? • Mod Alamat (later…) • RISC v CISC

Jenis 2 Operan • Alamat 2. • Nombor 2. – Integer/floating point. • Characters. – ASCII etc. • Data Logikal. – Bits or flags. • (Aside: is there any difference between numbers and characters? Ask a C programmer!).

Pentium Data Types • • • 8 bit byte 16 bit word 32 bit double word 64 bit quad word Addressing is by 8 bit unit A 32 bit double word is read at addresses divisible by 4

Specific Data Types • • • General - arbitrary binary contents Integer - single binary value Ordinal - unsigned integer Unpacked BCD - one digit per byte Packed BCD - 2 BCD digits per byte Near pointer - 32 bit offset within segment Bit field Byte string Floating point

Jenis 2 Operasi • • Perpindahan data (Data transfer) Aritmetik Logikal Pertukaran (Conversion) I/O Kawalan sistem (System control) Transfer of control

Perpindahan Data • Tentukan – Sumber (Source) – Destinasi (Destination) – Amount of data • Berkemungkinan arahan yg berbeza utk permindahan yg berbeza – E. G. IBM 370 • Atau satu arahan dan berlainan alamat – E. G. VAX

Aritmetik • • Tambah, tolak, darab, bahagi Integer bertanda Titik apungan? Mungkin juga termasuk – Increment (a++) – Decrement (a--) – Negate (-a)

Shift and Rotate Operations

Logikal • Bit wise operations • And, or, not

Pertukaran • Cth. Binary to decimal

Input/output • Mungkin ada arahan spesifik • Mungkin dilakukan m’gunakan arahan peralihan data (memory mapped) • Mungkin dilakukan oleh controller (DMA) yg terasing.

Kawalan Sistem • Arahan terlindung • CPU perlu berada dlm situasi tertentu – Ring 0 on 80386+ – Kernel mode • Utk kegunaan OS

Permindahan Kawalan • Cabang (Branch) – E. G. Branch to x if result is zero • Langkau (Skip) – – E. G. Increment and skip if zero ISZ register 1 Branch xxxx Add a • Panggil subrutin (Subroutine call) – C. F. Interrupt call

Pentium Floating Point Data Types • See Stallings (5 th Ed - Chapter 9, 6 th Ed – Chap 10) / Instruction Sets: Characteristics and Function