Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 7/19/2024
Public
Document Table of Contents

5.10.6.7.1. Glue Logic for Master Port ss_in_n

When configured as a master, the SPI has an input, ss_in_n. The polarity of this signal depends on the serial protocol in use, and the protocol is dynamically selectable.

Glue logic is required if both of the following conditions are met:

  • The serial protocol must be changed dynamically
  • One of the protocols being used is SSP

Glue logic is not required under either of the following conditions:

  • If dynamically changing the protocol that the SPI master is operating under is not necessary
  • If the serial protocol is changed dynamically, but the SSP protocol is not used.

The table below lists the three protocols and the effect of ss_in_n on the ability of the master to transfer data. Note that for the SSP protocol the effect of ss_in_n is inverted with respect to the other protocols.

Table 273.   ss_in_n Value Setting For Different Protocols

Protocol

ss_in_n value

Effect on Serial Transfer

Motorola SPI

1

Enabled

0

Disabled

National Semiconductor Microwire

1

Enabled

0

Disabled

Texas Instruments Synchronous Serial Protocol (SSP)

1

Disabled

0

Enabled

Figure 227. SPI Configured as Master Device