Arria V Hard Processor System Technical Reference Manual

ID 683011
Date 12/02/2022
Public
Document Table of Contents

20.4.2. SPI Controller Overview

In order for the SPI controller to connect to a serial‑master or serial‑slave peripheral device, the peripheral must have a least one of the following interfaces: †

  • Motorola SPI protocol – A four‑wire, full‑duplex serial protocol from Motorola. The slave select line is held high when the SPI controller is idle or disabled. For more information, refer to “Motorola SPI Protocol”. †
  • Texas Instruments Serial Protocol (SSP) – A four‑wire, full‑duplex serial protocol. The slave select line used for SPI and Microwire protocols doubles as the frame indicator for the SSP protocol. For more information, refer to “Texas Instruments Synchronous Serial Protocol (SSP)”. †
  • National Semiconductor Microwire – A half‑duplex serial protocol, which uses a control word transmitted from the serial master to the target serial slave. For more information, refer to “National Semiconductor Microwire Protocol”. You can program the FRF (frame format) bit field in the Control Register 0 (CTRLR0) to select which protocol is used.  †

The serial protocols supported by the SPI controller allow for serial slaves to be selected or addressed using hardware. Serial slaves are selected under the control of dedicated hardware select lines. The number of select lines generated from the serial master is equal to the number of serial slaves present on the bus. The serial‑master device asserts the select line of the target serial slave before data transfer begins. This architecture is illustrated in part A of the Hardware/Software Slave Selection figure. †

When implemented in software, the input select line for all serial slave devices should originate from a single slave select output on the serial master. In this mode it is assumed that the serial master has only a single slave select output. If there are multiple serial masters in the system, the slave select output from all masters can be logically ANDed to generate a single slave select input for all serial slave devices. †

The main program in the software domain controls selection of the target slave device; this architecture is illustrated in part B of the Hardware/Software Slave Selection figure below. Software would control which slave is to respond to the serial transfer request from the master device. †

Figure 87. Hardware/Software Slave Selection