SPI and UART timeout description lacking in RP2350 datasheet

[JamesH65]

From a customer:

In the document “RP2350 Datasheet”, build version 3184e62-clean, table 1104, the description of bit RTIM reads:

"RTIM: Receive timeout interrupt mask: 0 Receive FIFO not empty and no read prior to timeout period interrupt is masked. 1 Receive FIFO not empty and no read prior to timeout period interrupt is not masked."

It doesn’t state how long the timeout actually is. I poked around and didn’t find it stated anywhere else in the document. When set to 16 bit frames it's 32 SPI clocks. I didn’t check if the timeout changes with the frame size which might imply that it’s two frames rather than 32 bits.

The RP2040 data sheet appears to have the same deficiency. I didn’t dig too deep but the timeout for the UART doesn’t appear to be specified, either. We often have cases where the timing is strict to keep communication moving as quickly as possible so it’s important to know exactly how many clocks elapse before a timeout event.

[JamesH65]

@lurch FYI.

[lurch]

@JamesH65 IIRC the UART peripherals in RP2040 and RP2350 are Arm PL011 https://developer.arm.com/documentation/ddi0183/latest/ and the SPI peripherals are Arm PL022 https://developer.arm.com/documentation/ddi0194/latest/

I had a bit of a rummage and I see that section 12.1.6.4 in the RP2350 datasheet (within the UART section) says "The receive timeout interrupt is asserted when the receive FIFO is not empty and no more data is received during a 32-bit period" which seems to correspond to https://developer.arm.com/documentation/ddi0183/g/functional-overview/interrupts/uartrtintr?lang=en in the PL011 docs.
The PL022 docs contain https://developer.arm.com/documentation/ddi0194/h/programmer-s-model/interrupts/ssprtintr which says "The receive timeout interrupt is asserted when the receive FIFO is not empty and the PrimeCell SSP has remained idle for a fixed 32 bit period. ", but that info appears to be missing from the RP2350 datasheet. @nickfrancis55 Is this something that needs to be added? (to the SPI sections in both the RP2040 and RP2350 datasheets)