Shift Register Serial Communication System Digital

Pokok Bahasan Shift Registers MSI Shift Registers Komunikasi Serial Definisi Model I/O : Serial, Pararel dan Kombinasi Arah pergeseran : Kiri, Kanan dan dua arah Applikasi/penggunaan Implementasi VHDL MSI Shift Registers Komunikasi Serial D Q Input Clock Q3 Q2 Q1 Q0 Enable Output

Shift Registers Memanfaatkan register untuk penyimpanan, manipulasi dan transfer (pemindahan) data

Definisi Register adalah sebuah rangkaian digital dengan dua (2) fungsi utama : Data storage dan Data Movement Shift register menyediakan fungsi data movement A shift register “shifts” its output once every clock cycle Shift register adalah sekelompok flip flop yang dipasang secara linier dengan masukan dan keluaran saling disambungkan satu dengan yang lain, sehingga data akan digeser dari satu alat ke alat yang lain ketika rangkaian tersebut diaktifkan

Pemanfaatan Shift register Komunikasi UART -> Universal asynchronous receiver/transmitter Konversi antara serial dan pararel Penyimpanan sementara di processor scratch-pad memories Operasi Aritmatika Perkalian, pembagian Applikasi counter Johnson counter ring counter LSFR counters time delay devices more …

Shift Register Characteristics Tipe Serial-in, Serial-out Serial-in, Parallel-out Parallel-in, Serial-out Parallel-in, Parallel-out Universal Arah Left shift Right shift Rotate (right or left) Bidirectional n-bit shift register

Data Movement Bit – bit dalam shift register dapat digeser sesuai gambar dibawah ini

Data Movement Blok diagram shift register dengan berbagai variasi input/output n-bit shift register n-bit shift register n-bit shift register n-bit shift register

Serial-In Serial-Out n-bit shift register Bit data masuk satu persatu dan keluar satu per satu Satu flip flop bertugas untuk menyimpan satu data Pergerakan data dapat geser kiri / kanan, pada umumnya satu register hanya bisa satu arah. Masukan Asynchronous preset dan clear digunakan untuk set nilai awal

Serial-In Serial-Out Rangkaian logika ini menunjukkan gambar secara umum Serial in Serial Out Shift Register Menggunakan SR Flip Flop Dirangkai sehingga memiliki perilaku seperti flip-flop D Nilai masukan input akan digeser ke setiap flip-flop berpadanan dengan clock pulse N-Bit Shift Register N 1

Shift Registers Shift register paling sederhana hanya menggunakan flip-flops Keluaran dari flip-flop disambungkan dengan masukan D pada flip- flop berikutnya di sebelah kanan Setiap pulsa clock akan menggeser nilai register satu bit satu posisi ke sebelah kanan Serial input (SI) menentukan status masukan Flipflop paling kiri pada saat terjadinya pergeseran, Serial output (SO) diambil dari keluaran flipflop paling kanan Perhatikan animasi Q

Serial-In Serial-Out Cara paling mudah untuk mempelajari adalah lihat ilustrasi pada sebelah kanan 4 bit data word “1011” akan di geser pada 4 bit shift register One shift per clock pulse Data di tunjukkan masuk dari sisi sebelah kiri dan keluar dari sisi kanan 1 2 3 4 5

Serial-In Serial-Out Diagram di sebelah kanan menunjukkan urutan 4 bit “1010” di load ke 4 bit SISO shift register Setiap bit akan bergeser 1 posisi ke sebelah kanan pada setiap terjadi clock leading edge dibutuhkan 4 pulsa clock untuk memasukkan seluruh bit ke register.

Serial-In Serial-Out Diagram disebelah kanan menunjukkan urutan 4 bit “1010” unloaded dari 4 bit SISO shift register Setiap bit akan bergerak satu bit ke kanan setiap signal clock Dibutuhkan 4 clock untuk mengakhiri proses tersebut.

Serial-In Serial-Out SISO di pergunakan untuk komunikasi data : RS-232 modem transmission and reception Ethernet links SONET etc.

Serial-In Serial-Out in VHDL Berikut ini adalah kode program implementasi VHDL untuk 8 bit shift register pada positif edge clock Serial in Serial Out library ieee; use ieee.std_logic_1164.all; entity shift is port(C, SI : in std_logic; SO : out std_logic); end shift; architecture archi of shift is signal tmp: std_logic_vector(7 downto 0); begin process (C) begin if (C'event and C='1') then for i in 0 to 6 loop tmp(i+1) = tmp(i); end loop; tmp(0) = SI; end if; end process; SO = tmp(7); end archi;

Konversi Serial-to-Parallel n-bit shift register Konversi serial ke pararel dibutuhkan pada saat Misal setelah menerima transmisi data secara serial Ilustrasi 4 bit serial in pararel out Shift register di gambarkan di sebelah kanan Output Q pada flipflop paling kanan juga dapat berfungsi sebagai serial out.

Serial-to-Parallel Conversion Digunakan serial in pararel out shift register sepanjang N untuk mengubah N bit word dari serial ke pararel. Di butuhkan pulsa N clock untuk load dan 1 clock pulse untuk unload

Serial-to-Parallel Conversion Dua buah shift register di sebelah kanan digunakan konversi serial data ke pararel data Register bagian bawah akan menyediakan untuk register bagian atas, ketika di geser oleh register bag bawah

Parallel-to-Serial Conversion n-bit shift register Data di applikasikan ke bentuk pararel, kemudian di umpan masukkan ke Pin A hingga D. Kemudian dibaca secara sequential pada register 1 bit pada satu waktu dari PA ke PD setiap 1 siklus clock dalam bentuk serial Satu pulsa clock untuk load Empat pulsa clock untuk unload

Parallel-to-Serial Conversion Logic circuit for a parallel-in, serial-out shift register 1 1 Mux-like 1

Parallel-In Parallel-Out Parallel-in Parallel-out Shift Registers can serve as a temporary storage device or as a time delay device The DATA is presented in a parallel format to the parallel input pins PA to PD and then shifted to the corresponding output pins QA to QD when the registers are clocked One clock pulse to load One pulse to unload

Universal Shift Register Can do any combination of parallel and serial input/output operations Requires additional inputs to specify desired function Uses a Mux-like input gating n-bit shift register L/S A B F 1 1

Universal Shift Register Parallel-in, parallel-out shift register 1 1 Mux-like 1

Universal Shift Register Parallel shift register (can serve as converting parallel-in to serial-out shifter):

MSI Shift Registers 74LS164 is an 8-Bit Serial-In Parallel-Out Shift Register Typical Shift Frequency of 35 MHz Asynchronous Master Reset Gated Serial Data Input Fully Synchronous Data Transfers

MSI Shift Registers 74LS164 8-Bit Serial-In Parallel-Out Shift Register

MSI Shift Registers The 74LS164 is an edge-triggered 8- bit shift register with serial data entry and an output from each of the eight stages. Data is entered serially through one of two inputs (A or B); either of these inputs can be used as an active HIGH Enable for data entry through the other input an unused input must be tied HIGH, or both inputs connected together

MSI Shift Registers Each LOW-to-HIGH transition on the Clock (CP) input shifts data one place to the right This also enters into Q0 the logical AND of the two data inputs (A•B) that existed before the rising clock edge.

MSI Shift Registers 74LS164 logic diagram A LOW level on the Master Reset (MR) input overrides all other inputs and clears the register asynchronously, forcing all Q outputs LOW.

MSI Shift Registers 74LS166 is an 8-Bit Shift Register Parallel-in or serial-in shift/load input establishes the parallel-in or serial-in mode Serial-out Synchronous Load Serial data flow is inhibited during parallel loading Direct Overriding Clear

MSI Shift Registers 74LS166 is an 8-Bit Shift Register

MSI Shift Registers 74LS166 8-Bit Shift Register is a parallel-in or serial-in, serial-out shift register

MSI Shift Registers 74LS166 is an 8-Bit Shift Register

MSI Shift Registers 74LS166 is an 8-Bit Shift Register

MSI Shift Registers 74LS194 4-Bit Bidirectional Universal Shift Register may be used in serial-serial, shift left, shift right, serial-parallel, parallel-serial, and parallel-parallel data register transfers

MSI Shift Registers 74LS194 4-Bit Bidirectional Universal Shift Register

MSI Shift Registers 74LS194 control inputs S1 and S0

MSI Shift Registers 74LS194 4-Bit Bidirectional Universal Shift Register 01 11 10 00 01 11 10 00 01 11 10 00 01 11 10 00

MSI Shift Registers 74LS194 4-Bit Bidirectional Universal Shift Register

“Universal” shift register 74x194 Shift left Shift right Load Hold

MSI Shift Registers One stage of the 74x194

VHDL Dhift Register Universal shift register design The 3-bit function select determines the operation of the register Serial in and Parallel load available library IEEE; use IEEE.std_logic_1164.all; use IEEE.std_logic_unsigned.all; entity Vshftreg is port (CLK, CLR, RIN, LIN: in STD_LOGIC; S: in STD_LOGIC_VECTOR (2 downto 0); -- function select D: in STD_LOGIC_VECTOR (7 downto 0); -- data in Q: out STD_LOGIC_VECTOR (7 downto 0) -- data out); end Vshftreg; architecture Vshftreg_arch of Vshftreg is signal IQ: STD_LOGIC_VECTOR (7 downto 0); begin process (CLK, CLR, IQ) if (CLR='1') then IQ <= (others=>'0'); elsif (CLK'event and CLK='1') then case CONV_INTEGER(S) is when 0 => null; -- Hold when 1 => IQ <= D; -- Load when 2 => IQ <= RIN & IQ(7 downto 1); -- Shift right when 3 => IQ <= IQ(6 downto 0) & LIN; -- Shift left when 4 => IQ <= IQ(0) & IQ(7 downto 1); -- Shift circular right when 5 => IQ <= IQ(6 downto 0) & IQ(7); -- Shift circular left when 6 => IQ <= IQ(7) & IQ(7 downto 1); -- Shift arithmetic right when 7 => IQ <= IQ(6 downto 0) & '0'; -- Shift arithmetic left when others => null; end case; end if; Q <= IQ; end process; end Vshftreg_arch;

MSI Shift Registers 74LS299 is an 8-bit universal shift/storage register with 3-state outputs Four modes of operation are possible: hold (store) shift left shift right load data

MSI Shift Registers 74LS299 universal shift/storage register

MSI Shift Registers 74LS299 universal shift/storage register S0 S1 D Q CP CD

MSI Shift Registers 74LS299 logic circuit diagram: The parallel load inputs and flip-flop outputs are multiplexed to reduce the total number of package pins. Separate outputs are provided for flip-flops Q0 and Q7 to allow easy cascading. A separate active LOW Master Reset is used to reset the register.

Serial Communications A practical application of Registers / Shift Registers

Serial data systems (e.g., TPC) Read discussion and study circuits in text.

Serial Data Transmission Parallel-to-serial conversion for serial transmission in: parallel data out: parallel data Source module Destination module serial transmission media

Serial data in the phone system (E-1) 2.048 Mb/s links between phone switches and subscribers partitioned into 32 64 Kb/s channels Each channel gets a timeslot in a “frame” where it can send 8 bits every 125 sec. 8000 frames/sec

Timeslot details count = 255

Parallel-to-serial conversion 256 Parallel-to-serial conversion LSBs are bit number Assert shift-register LOAD input during bit 7 Timeslot number can be decoded and used to select source of parallel data count = 255 Serial data to destination

Serial-to-parallel conversion Synchronize destination’s counter to source’s Serial-to-parallel conversion Detect that a complete byte has been received Note: loads 0…0 Holding register for complete byte Shift in serial data

Destination timing Grab complete byte when available Serial-in, parallel-out shift register outputs Holding-register outputs Grab complete byte when available

Serial communication on ONE wire Serial communication requires three signals: CLOCK, SYNC, and DATA. Yet only one “wire” is used. How? One solution: Manchester code. Or use a phase-locked loop (analog circuit) to extract clock from the data:

Still a couple of problems Framing -- SYNC signal Solution: Use a unique data pattern for SYNC PLL clock recovery -- what if too many zeroes are transmitted? PLL can’t stay in sync. Solution: Use a code that guarantees a minimum number of ones Phone system: Map 00000000 --> 00000010 (creating slight voice distortion) Gigabit Ethernet: Uses 8B10B code, solving both problems Map each byte into 8 bits Use only a “good” subset of 210 code words Use another code word for synchronization

Assignments Completed Part 2 Midterm problems due Wednesday Continue working on the MIPS project Description available on the course web page