Relation between SPI, clock rate and data bits in microcontroller

Question

I am working on a project which requires a UHF RFID Reader IC AS3993 having an 8 bit Reader MCU. And an externally connected LaunchPad (SimpleLink LAUNCHXL CC3200) for data transfer which works at 16 bit/32 bit.

But, the reader IC and external LaunchPad have different clock rates and different bit rates. Then I would like to know how can I ensure proper data transfer using SPI (Serial Peripheral Interface) between Launchpad and AS3993, despite having different clock rates and different bit rates.

Reference links:

• LaunchPad CC3200 LAunchXL technical and related documents
• AS3993 Block Diagram
• AS3993 datasheet

• David: At least one of your links is bad. Can you link to the actual datasheets instead of a file hosting service (2shared) ?

Answer 1

SPI uses synchronous communication, i.e. the device which originates traffic (the master) sends clock to the slave. As long as the clock rate is not higher then quarter of sampling frequency at the slave, any frequency can be used.

Architecture of communicating processors has no significance, if both sides can work with same word length (all should be able to do 8-bit SPI).

What has to match, is the SPI mode. It describes clock polarity (CPOL) and clock phase (CPHA). Most common mode is 00 (clock idle low, data out at falling edge, data in at rising edge).

• carveone: Also bear in mind that different manufacturers have different ideas about mode. PIC microcontrollers for example. What's important is to check the timing diagram very carefully.