Shift register SPI

DVDdoug: The 164 isn't a shift register, but it's flip-flops can be wired as a shift register. The overall design allows you to shift-in a data pattern and then send/latch that output state to all of the outputs at once. If you use the 164 the data will show-up at the outputs as it's shifted-through. If I want to turn-on one LED at the end of the chain, I have to turn-on all of the LEDs one at a time, 'till it gets to the end of the shift register. (That could happen very fast so. The SHIFT REGISTER clock to SCK, the DATA INPUT to SDO (on the first IC only), and the OUTPUT REGISTER clock to another PIC pin. For every transfer I do: 1. Set RESET HIGH then LOW 2. Send data out SPI 3. Set OUTPUT REGISTER clock HIGH then LOW This works, except for a small detail: ONE bit of every 8 bits (one SPI transfer) is lost. The DATA is not sent but the CLOCK is correct (because it sends the right number of CLOCK pulses but there's one missing DATA bit which is always. I'm currently using my SPI for my SD card, but also want to use it for a shift register (three chained actually) that I use for addressing a 512K SRAM. (So very slow at present). The shift register is the latchless cd74hc164 chip. So if I connect my serial pin to MOSI and my clock pin to SCK how do I configure CS into the mix? What would that even signify as it's not like the device itself can actually select? What would it's purpose actually be? I'm not planning on using.. TL;DR: You can't use Shift Registers over SPI to control the Slave Select of SPI devices on the same bus because you'll end up sending the commands for the Shift Registers to the other devices when you want to disable them. The table at the bottom sets out the flow and why it breaks, and the words between here and there is my tale of woe, and a bunch of useful details Shift registers deal with both serial and parallel data on both their inputs and outputs and they can convert between these formats. There are four basic types of shift registers: Serial In - Parallel Out. The Serial In - Parallel Out (SIPO) shift register converts serial data to parallel data. It is used in communications and to drive multiple output ports using serial data

esp32 shift-register spi stm32. While working on a circuit, I am confused on connecting daisy chained 74HCT595 and 74HCT165 to microcontroller. I am developing the circuit so that microcontroller can be connected as separate add-on module. I am planning to use: ESP32; STM32; The confusion is that the Shift-Registers refer to SPI communication on some internet sources while others say it is not. The SPI is built around a double buffered 8-bit shift register with both ends of the shift register brought out to MCU pins. One end of the shift register is connected to the master-in slave-out pin, MISO. This pin acts as an input for the master SPI Module and as an output for the slave SPI Module. The other end of the shift register is connected to MOSI pin SIPO Vs PISO Shift Registers. Shift registers come in two basic types, either SIPO (Serial-In-Parallel-Out) or PISO (Parallel-In-Serial-Out). The popular SIPO chip is 74HC595, and the PISO chip is 74HC165. The first type, SIPO, is useful for controlling a large number of outputs, like LEDs. While the latter type, PISO, is good for gathering a large number of inputs, like buttons; like the one used in Original Nintendo Controller as discussed above

SPI Bus In-Depth using the Particle Xenon and a 74HC595Off-the-shelf TFT modules suit handheld electronic devices

SPI •Overview • 8 bit synchronous shift register used to communicate externally • Most often used to communicate with peripherals • displays, sensors, converters • Can be used for inter-processor communication • Two modes of operation • Master -responsible for providing the clock • Slave -receives clock from the maste AVR-Tutorial: Schieberegister. Ab und an stellt sich folgendes Problem: Man würde wesentlich mehr Ausgangspins oder Eingangspins benötigen als der Mikrocontroller zur Verfügung stellt. Ein möglicher Ausweg ist eine Porterweiterung mit einem Schieberegister. Zwei beliebte Schieberegister sind beispielsweise der 74xx595 bzw. der 74xx165 The Arduino Uno communicates with the shift register using SPI . The Arduino is the Master and the shift register is the Slave. For this purpose we need the Data (MOSI), Clock (SLCK) and Latch (Slave Select) pins connected. The MISO (Master In Slave Out) line is not needed because we are not going to read any data from the LCD The SPI operation is based upon shift registers. Every device, whether Master or Slave has an 8-bit shift register inside it. The size of the shift register could be more than 8-bit as well (like 10-bit, 12-bit, etc), but it should be the same for both Master and Slave, and the protocol should support it. Hardware Setu SHCP = SHift Clock Pin ist der Clock-Eingang zur Übernahme des Data Signals in das eigentliche Schieberegister (Shift Register). STCP = STore Clock Pin - Der Wechsel von Low auf High kopiert den Inhalt des Shift Registers in das Ausgaberegister bzw

SPI with shift registers 595 questions - General

Most of their offerings have an SPI module, or Serial Peripheral Interface. A shift register is exactly that, a peripheral device that communicates via a serial line. All we need to do is hook up our connections and use a few pieces of simple code. Join me after the break to see how that's done Ein Schieberegister ist ein logisches Schaltwerk. Mehrere in Reihe geschaltete Flipflops schieben ihren Speicherinhalt bei jedem Arbeitstakt um ein Flipflop weiter - anschaulich gesehen ähnlich einer Eimerkette. Die Anzahl der im Register vorhandenen Speicherplätze ist konstant. Schieberegister arbeiten nach dem FIFO-Prinzip. Das zuerst eingespeicherte Bit verlässt den Speicher zuerst. Das Herein- und Herausschieben, das Ein- und das Auslesen geschehen dabei synchron, ein. Driving shift registers with AVR SPI. Contribute to szczys/Shift-Registers-SPI development by creating an account on GitHub Controlling a 74HC595 shift register via SPI. While other shift registers can also be controlled, the SPI compatible 74HC595 has a big advantage over a normal shift register in that it is about 10 times faster (ATmega328). This is noticeable with a larger multiplex. The following functions are described in other tutorials: GPIO - Output / Input - How do I make a GPIO access on the AVR. SPI.

So, I was thinking if any of you tried to use a shift register with the AVR's SPI/USI interfaces? If so, could you please give me some hints or a reference from where I can start? Thank you very much for you time, regards, AP. Tags: AVR Microcontrollers, megaAVR and tinyAVR. Log in / register to post comments; Top. clawson. Level: Moderator . Joined: Mon. Jul 18, 2005 . Posts: 101911 View. Serial Peripheral Interface (SPI) is an interface bus commonly used to send data between microcontrollers and small peripherals such as shift registers, sensors, and SD cards. It uses separate clock and data lines, along with a select line to choose the device you wish to talk to

The core of the SPI is an 8-bit shift register in both the Master and the Slave, and a clock signal generated by the Master. Let's say the Master wants to send a byte of data (call it A) to the Slave and at the same time receive another byte of data from the Slave (call it B). Before starting the communication, the Master places A in its shift register, and the Slave places B in its shift. In this video we are going to use the SPI port to control a shift register 74hc595.The microcontroller used is the stm32f103c8 in the bluepill board What makes SPI so popular among other Synchronous Serial Communication protocols (or any serial communication for that matter) is that it provides a high speed secured data transfer with reasonably simple hardware like shift registers at relatively less cost. How SPI Works? SPI or Serial Peripheral Interface was developed by Motorola in the.

SPI to a shift register (74HC595) Microchi

  1. The 74HC595 is a serial-to-parallel shift register or SIPO (Serial In Parallel Out) device for increasing the number of outputs from your microcontroller. Its simply a memory device that sequentially stores each bit of data passed to it. You send it data by presenting a data bit at the data input and supplying a clock signal to the clock input
  2. Contrôle de 8 LEDs rouges à l'aide d'un shift register et d'un Arduino Mega. Utilisation de la bibliothèque SPI
  3. Shift register is controlled with three pins. They are usually called DATA, LATCH and CLOCK. Chip manufacturers have different names. See the table below for two examples from Texas Instruments
microcontroller - Shift Register Counter - Electrical

Shift Register SIPO ESP8266 NodeMCU Wiring between 74hc595n and ESP32 Boards The following picture shows the wiring between the ESP32 ESP-WROOM-32 and the 74hc595n shift register. For the power supply, you can use the 3.3V or 5V pin of the ESP32 microcontroller, because the operation voltage of the shift register is between 2V and 6V Shifts a byte -- 8 bits -- to the storage register. Assumes register bit length evenly divisible by 8. Pushes / overwrites any existing values. Latches by default. ShiftClear() Shifts zeros. Will dim all connected LEDs, for example. Assumes register bit length evenly divisible by 8. Supports GPIO controller or SPI device. Write(Byte The SPI Data Register is a read/write register used for data transfer between the Register File and the SPI Shift Register. Writing to the register initiates data transmission. Reading the register causes the Shift Register Receive buffer to be read Permanent Redirect.

The SPI is built around a double buffered 8-bit shift register with both ends of the shift register brought out to MCU pins. One end of the shift register is connected to the mast er-in slave-out pin, MISO. This pin acts as an input for the master SPI Module and as an output for the slave SPI Module. The other end of the shift register is connecte I'm trying to implement simple SPI driver in compatibility mode on TMS570 to do byte by byte transfer. I wish manually to drive the CS lines. No I have problem that after transefring last byte to SPIDAT0->TXDATA register I can't check when the data are moved from shift register. I can only check. ESP8266 Shift Register (74HC595) using the Arduino IDE and SPI - ESP8266-74HC595-SPI.ino. Skip to content. All gists Back to GitHub Sign in Sign up Sign in Sign up {{ message }} Instantly share code, notes, and snippets. 42Bots / ESP8266-74HC595-SPI.ino. Last active Dec 10, 2018. Star 0 Fork 2 Star Code Revisions 3 Forks 2. Embed. What would you like to do? Embed Embed this gist in your.

Using SPI with shift registers

Slave Select via SPI Shift Registers Chris Dawson

one clock cycle both 8-bit shift registers can be considered as one 16-bit circular shift register. This means that after eight SCK clock pulses the data between master and slave will be exchanged. Atmel AVR151: Setup and Use of the SPI [APPLICATION NOTE] Atmel-2585D-Setup-and-Use-of-the-SPI_AVR151_Application Note-02/2016 3. The system is single buffered in the transmit direction and double. Serial Peripheral Interface (SPI) is one of the most widely used interface between microcontroller and peripheral ICs such as sensors, ADCs, DACs, Shift register, SRAM etc. This article provides a brief description of the SPI interface followed by introducing Analog Devices' SPI enabled switches and muxes and how they help reduce number of digita SPI consists of two shift register, one in the master device and the other in the slave device. Serial-out of the master shift register is connected to serial-in of slave shift register via MOSI pin. Serial-out of the slave shift register is connected to serial-in of master shift register via MISO pin. On a clock edge, both master and slave shifts out 1 bit data ( most significant bit (MSB. So you would be bit-banging SPI to shift register acting as IO expander, and then use the IO expander to bit-bang SPI to SPI Flash chip, which makes very little sense. It would make more sense to use the bit-banged SPI to the HC595 also for the SPI flash, you only need separate chip selects (and data back from flash) I/O or peripheral expansion via devices such as shift registers, display drivers, SPI EPROMS, and analog-to-digital converters. 1.2 Terminology Used in This Document Table 1-1 defines the important acronyms used in this document. 1.3 Features The SPI has the following features: • 16-bit shift register • 16-bit Receive buffer register (SPIBUF) and 16-bit Receive buffer emulation alias.

Arduino - ShiftOut

Shift Registers - 74HC595 & 74HC165 with Arduin

This is done by using a technology called Serial Peripheral Interface (SPI) which uses a synchronous serial data protocol to communicate with 74HC595 IC. In here Arduino micro controller acts as the master device and shift register acts as the slave device. LCD display is connected to the outputs of the Shift register IC Die SPI Version hat einen grossen Vorteil gegenüber einem normalen Schieberegister, das sie etwa den Faktor 10 schneller ist (ATmega328). Dies macht sich bei einem grösseren Multiplex bemerkbar. Die folgenden Funktionen, sind in folgenden Tutorials beschrieben: GPIO - Aus / Ein-gabe - Wie mache ich einen GPIO-Zugriff am AVR Receive Shift Register Transmit Buffer UCxTXBUF Transmit Shift Register SPI Receive Buffer Data Shift Register DSR UCx SOMI SOMI MASTER SIMO UCxSIMO SLAVE Px.x UCxSTE STE SS Port.x SCLK UCxCLK COMMON SPI MSP430 USCI www.ti.com USCI Operation - SPI Mode SLAU411F-August 2012-Revised March 2018 7 Submit Documentation Feedbac

Shift Register 74HC595: Here is the pin out diagram of the 74HC595 as per the datasheet-. HC595 has 16pins; if we see the datasheet we will understand the pin functions- The QA to QH, from pin numbers 1 to 7 and 15 used as 8 bit output from the shift register, where as the pin 14 is used for receiving the serial data.There is also truth table about how to use other pins and avail other. Using a shift register I am able to shift in all the data via a single data line and a single clock line, and then control all 29 transistors using the outputs of the shift registers. The only issue with this is that as the data is shifted in, the displays will scramble as the data will change every time a bit is added. This can be overcome using a combined shift-register and latch such as the.

Index > MobiFlight General > Shift register. Message #23716. captt. Posts: 2. First of all thank you very much for your great piece of software. With the new version 9 I saw that it is possible to use shift registers but limited to ICs supporting SDI/SPI protocoll. I have here finished PCB Boards equipped with IC's MCP23017 driven by I²C protocoll. So is it planned to also support that type. select line goes low, data to be transmitted should be placed in the master's SPI data register. The SPI Transmit Data register (TxDATA) and SPI Receive Data register (RxDATA) share the same I/O address, referred to as the SPI Data register (DATA). Writing DATA register will update the Transmit Data register. Reading the DATA register will return the content of the Receive Data register. A shift register implements a FIFO of fixed length. Every time a new element enters the queue, it shifts the existing ones one place further away from the input. To understand the basics of the shift register, I recommend viewing the VHDL tutorial about the std_logic_vector. This article will only consider the shift register, even though there exist data structures that use fewer resources for.

Electronic - Properly connecting Shift-Registers to

The objective of this post is to explain how to connect the SN74HC595 8-bit shift register to an ESP8266 to control some LEDs. The code to interface with the device is also explained. We assume the use of the ESP8266 libraries for the Arduino IDE. You can check here how to configure the Arduino IDE to support the ESP8266 The shift register accepts serial data and provides a serial output. The shift register also provides parallel data to the 8−bit latch. The shift register and latch have independent clock inputs. This device also has an asynchronous reset for the shift register. The HCT595A directly interfaces with the SPI serial data port on CMOS MPUs and. This lets you use any pins for the shift register, perhaps keeping the SPI pins free for an SD card or other device. // Demo sketch to read from a 74HC165 input shift register // Author: Nick Gammon // Date: 23 March 2013 // Pin connections for Uno and similar: // Chip pin 1 (/PL) goes to LATCH (D8) // Chip pin 2 (CP) goes to SCK (D7) // Chip pin 9 (Q7) goes to MISO (D6) #include <bitBangedSPI. 74HC595 Shift Register Interfacing with Arduino. 74HC595 IC is a 16-pin shift register IC consisting of a D-type latch along with a shift register inside the chip. It receives serial input data and then sends out this data through parallel pins. In addition to parallel outputs, it also provides a serial output You might use the SPI peripheral of the STM32F0 for your task. When configured in slave mode, each time an external clock edge is detected on the SCK signal, the MISO will be set to the next bit of a value loaded into an internal shift register via the SPI data register. Check out the chapter on the Serial peripheral interface (SPI) in STM32F0.

74HC595 Shift Register With Arduino Uno: Recently I started project that uses 74HC595 shift register. So I wondered what is the most efficient way to transfer data to it. As 74HC595 utilizes serial interface, all what I learned will apply as well for any device that utilizes serial inter The shift register has direct overriding clear, serial input, and serial output (standard) pins for cascading. Both the shift register and storage register use positive edge triggered clocks. If both clocks are connected together, the shift register state will always be one clock pulse ahead of the storage register. All inputs are equipped with protection circuits against static discharge and. The matrix driver object uses SPI to send the bits to the shift register. Since the rows on the matrix are multiplexed when rendering, the matrix driver object will use a system clock interrupt to ensure the multiplexing is consistently timed. When constructing a matrix driver, you need to tell it a few details: The matrix's size in rows and columns; Whether the shift registers used for. I'm quite new to Arduino world and I'm trying to understand how shift registers work. I built this construction : In fact, it is an Arduino Duemilanove with AtMega on it, but afaik it doesn't matter. The tutorial I try to follow use SPI library so I try to do it too. I kind of understood that data input, latch and clock had to be pins 7, 4 and 11

SPI Device. Hope you got the basic idea of an SPI bus. Now let's see in little more detailed level like how it is working in hardware level. SPI having relatively very simple hardware compared to other serial communication protocols like UART, I 2 C etc. Its operation is based on shift registers (usually 8 bit) Shifts out a byte of data one bit at a time. Starts from either the most (i.e. the leftmost) or least (rightmost) significant bit. Each bit is written in turn to a data pin, after which a clock pin is pulsed (taken high, then low) to indicate that the bit is available. Note- if you're interfacing with a device that's clocked by rising edges. The data pin of the 74HC595 shift register is named DS (#14) and it is connected to Arduino pin 6. ST_CP (or RCLK) and SH_CP (or SRCLK) are connected together which then connected to Arduino pin 7. This is the clock pin. Since the display has 4 digits there're 4 common pins: 1 (most left), 2, 3 and 4. Each common pin is connected to collector terminal of one transistor. Emitter terminals of.

In-Depth: How 74HC595 Shift Register Works & Interface

AVR-Tutorial: Schieberegister - Mikrocontroller

五一电子阅读:《常用资料》—《74HC595 的实际应用与编程

The core idea of SPI is that each device has a shift-register that it can use to send or receive a byte of data. These two shift registers are connected together in a ring, the output of one going to the input of the other and vice-versa. One device, the master,controls the common clock signal that makes sure that each register shifts one bit in just exactly as the other is shifting one bit. ATMega32 SPI interfaces to 74HC165 and 74HC595 shift registers. Reading a digital data from 74HC165, and sending the data to 74HC595 shift registers doesn't always require the SPI module of the MCU. Using a software bit-banging could make this job done by a dozen lines of code. However, using the bit-banging method could make some timing delay.

Arduino controlled LCD using a shift register and the SPI

The registers provide an interface to the SPI core and are visible via the Avalon-MM slave port. The sclk, ss_n, mosi, and miso ports provide the hardware interface to other SPI devices. The behavior of sclk, ss_n, mosi, and miso depends on whether the SPI core is configured as a master or slave. Figure 9-1 shows a block diagram of the SPI core in master mode. Figure 9-1. SPI Core Block. slave shift register by MISO (Master In Slave Out) • After 8 clock pulses, the contents of the two shift registers are interchanged. University of Tehran 10 SS pin in SPI • Slave Select (SS) pin of the SPI bus is used to select a slave to initiate and terminate the data transfer • Makes sense in devices connected to several slaves • In master mode: - SS=0: enable slave - SS=1. The shift register diagram shows a generic layout for a simple bus. If you want to learn more about SPI, I highly recommend the Wikipedia page on the subject. It's excellent. SPI has 4 modes, depending on the CPHA and CPOL settings. We're just gonna talk about SPI mode 0, or when both CPOL and CPHA are 0. Lets jump into the Verilog. Parameter SPI PHY Implemented as a simple shift register: spi_phy.vhd SPI MAC Provides a parallel interface to a higher layer with appropriate control signals. This controller loads the PHY with the parallel data and sends out n clock pulses, where n corresponds to the number of bits in the parallel data, to the PHY to clock the transfer: spi_controller.vh

Serial Peripheral Interface - SPI Basics » maxEmbedde

Hi @ all, since a few weeks im kinda struggling to write a Variable on the SPI Bus, adressing a Shift Register. For that i need to write in HEx to have better controll, of what the Register does. Now , ive been checking the forum since quiet a while and either im totally blind, or there hasnt anyone ever had that trouble (which is kind of hard to believe). anyhow herre is my code: writing on. SPI TFT screen using 6522 VIA shift register. 6502. Close. Vote. Posted by 6 minutes ago. SPI TFT screen using 6522 VIA shift register. 6502.

74HC595 Schieberegister » Aufbau & Funktionsweise erklär

A shift register in our use-case is a storage that can be serially fed with digital values. In case of the 74HC595 shift register, it outputs the last eight bits of data in parallel. The PWM carrier frequency, denoted as f carrier, is the frequency that at which PWM pulses are emitted. Its inverse value is the period Electronic - How to use ATmega328 SPI with a 31 bit shift register. atmega avr shift-register spi. I'm using an Allegro 6280 PWM LED driver for a project. This is a cool little IC except for the fact that it is a 31 bit long input register. This is no problem if I simply loop through my 31 bits and set the pin states accordingly, but I'm wanting to use the atmega's on-board SPI to speed. The bits to be shifted out are stored in the SPI data register, SP0DR, and are sent out most significant bit (bit 7) first. When bit 7 of the master is shifted out through MOSI pin, a bit from bit 7 of the slave is being shifted into bit 0 of the master via the MISO pin. After 8 clock pulses or shifts, this bit will eventually end up in bit 7 of the master. The least significant bit can be. procedure nrf_set_config (reg, data: uint8); begin PORTspi:= PORTspi and not (Pspi_cs); // CS setzen, ist beim Modul low-aktiv spi_fast_shift (cW_REGISTER or (cREGISTER_MASK and reg)); // Controlbyte senden spi_fast_shift (data); // Datenbyte senden PORTspi:= PORTspi or Pspi_cs; // CS löschen, ist beim Modul low-aktiv end; Es wird ein Byte zur Adressierung des Registers und ein Byte mit dem. These shift registers are usually of 8 bits size for both the master and the slave device. It usually forms a circular buffer consists of two shift registers. In order to transfer data, a master device initiates the active high clock signal to a slave device and the frequency of the clock signal is less than or equal to the operating frequency of a slave device

How to drive 595 shift registers with AVR hardware SPI

SPI is a synchronous communication protocol because the clock is shared by the master and slave. SPI is supported only multi-slave does not support multi-master and slaves are selected by the slave select signal. In SPI during the communication data is shifted out from the master and shifted into the slave vice- versa through the shift register A normal shift register has eight output connections that you can control. Daisy chaining effectively creates a 16-output connection. You can take this further to make 24 output, 32 output, and so on. How far can you go? Let me know when you get there. How to connect daisy chained shift registers . Let's compare the schematic diagram for one shift register and the schematic diagram for two. STM32 & OpenCM3 Part 2: SPI and DMA Thu, Sep 13, 2018 Companion code for this post available on Github. In the previous section, we covered alternate functions, and configured a log console over UART.This time, we'll take a look at the SPI peripherals available on the STM32F0, use them to quickly shift out data to some shift registers, and then demonstrate how to then offload that transfer. shift registers (Figure 2). While the master communicates with the selected slave, the two devices' shift registers connect in a ring, so both devices always simultaneously send and re- By Dariusz CaBan, PHD • silesian university of teCHnology Coding SPI software ThE SPI REquIRES ThREE wIRES FoR dATA TRAnSFER PLuS A dEvICE-SELECT SIgnAL. dESIgnERS CAn ImPLEmEnT PERIPhERAL CommunICATIonS. SPI Control Register (S0SPCR - 0xE002 0000) Bit Symbol Value Description 6 LSBF LSB First, controls in which direction each byte is shifted when transferred. 0 SPI data is transferred MSB (bit 7) first. 1 SPI data is transferred LSB (bit 0) first

Chapter 4: Using the Synchronous Serial Interface SPI

In one SPI clock cycle, the following operations are completed: 1) The host sends 1-bit data through the MOSI line, and the slave reads the 1-bit data through the line; 2) The slave sends 1-bit data through MISO line, and the host reads the 1-bit data through the line. This is achieved by a shift register. As shown in the figure below, the. In this example I use the SPI module of ATMega32 to work in master mode. I use three slaves identical device, 74HC595 shift register. These three devices are the same in operation. So It requires only three wires. Activating the slave select pin once, these three shift register latch the data to its output register 74HC595 Shift Register - 3 pack Add lots more outputs to a microcontroller system with chainable shift registers. These chips take a serial input (SPI) of 1 byte (8 bits) an It is possible to do simple read and writes over the SPI bus using the standard read() and write() system calls though - write() may be better to use for sending data to chains of shift registers, or those LED strings where you send RGB triplets of data. Devices such as A/D and D/A converters usually need to perform a concurrent write/read transaction to work Shift Register BRG (3) Pins Interface SPI Module AXI SPI Interrupt Notes: 1. The width of Tx FIFO, Rx FiFO, and Shift Register depends on the value of the generic, C_NUM_TRANSER_BITS. 2. The width of SS depends on the value of the generic C_NUM_SS_BITS. 3. BRG (Buad Rate Generator) SPI Ports SCK MISO MOSI SS(N) SPISEL AXI4 Lite DS742_01 (1) (2) (1) DS742 July 6, 2011 www.xilinx.com 3 Product. Status Register. The SPI slave can operate without using the status register. This register provides the user with information regarding the state of the slave component but is not required to use the component. The status register contains three status bits. The master can read, set, or clear these bits with transactions addressed to this register. During a transaction that reads or writes.