What You Need to Know About the Switching Frequency and Duty Cycles when Communicating with QSPI Chips

Question from the Customer:

I’m looking into used your Promira Serial Platform as a QSPI master to communicate with our chip. Before I get started, I’d to know these capabilities with the Promira platform:

  1. Our preferred QSPI format is listed below.  Are dummy cycles required?
    • No instruction cycle
    • 2-cycle of address
    • No alt cycle
    • 4-cycle data
  2. What is the maximum frequency of the GPIO's toggle rate?

Response from Technical Support:

QSPI Format and Duty cycles

Thanks for your questions! The Promira Serial Platform with SPI Active – Level 3 Application supports the format you described and dummy cycles are not required. If you need dummy cycles, they can be inserted as 0x00s in the MOSI data.

Maximum Switching Frequency of GPIO Signals

The switching frequency (toggle rate) of GPIO pins depends on the time to apply the line-by-line execution of your script. There are also latencies to consider:

  • The operating systems (OS) may add delay due to the internal overhead.
  • The Promira platform has a latency, which is caused by the Ethernet/USB link between the computer and the Promira platform.

Here is additional information about the speeds per SPI Active level:

Duty Cycle Bit Rates

Part of setting up bit rates is the duty cycle. Here is an example for switching GPIOs with 50% duty cycle:

ps_queue_gpio_set(queue, STATE0)
ps_queue_delay_ms(queue, on_time_in_ms)
ps_queue_gpio_set(queue, STATE1)
ps_queue_delay_ms(queue, off_time_in_ms)

When the duty cycle is 50%, on_time_in_ms = off_time_in_ms.

Configuring GPIO Signals

The STATE0 and STATE1 parameters are set in terms of bitmasks of the available GPIOs, which varies per SPI Active Level application. The level affects the number of GPIO pins that you can configure.

Note - the number of available GPIO pins is affected when Slave Select(s) is configured.

Additional resources that you may find helpful include the following:

We hope this answers your questions. If you have other questions about our software, host adapters or other Total Phase products, feel free to email us at sales@totalphase.com. You can also request a demo that is specific for your application.