On 2/27/2019 7:26 AM, Damien Dando wrote: > >> Sadly, the Decamux code is using state register 6, or you could use >> registers 4-7 for the GPIO values. But you can do an offset when >> performing the XIN/XOUT (set SHIFT_EN in the SPP register), so you can >> use any other chunk of 4 registers in the scratchpad (maybe R0-3?). > do you know how many PRU cycle it takes to set the SHIFT_EN bit in SPP reg.? > There is the list of timing here: > http://www.ti.com/lit/sprace8 but I don't know if SHIFT_EN is considered as a > "PRU CTRL" register, "PRU CFG" or something else..
The SPP register is in the "PRU CTRL" domain. The latency doesn't really matter, the SPP write would be a one-time setup step at the start of the code. Usually, however, writes complete quickly as they do not need a response from the far end. The existing XIN/XOUT instructions will need to make sure r0.b0 is cleared first, but that's only one additional instruction per loop (the XOUT is a one-time setup step) and it allows much more flexible use of the scratchpad. > Also how long does it takes to load data from the PRU DRAM to > r0-31, the previous link say 3PRU cycles (15ns) but does that > depends of how many bytes we load? or it takes the same amount of > time regardless of the number of bytes? I believe it will take one extra clock for each additional DWORD read from the PRU data memory. -- Charles Steinkuehler char...@steinkuehler.net -- website: http://www.machinekit.io blog: http://blog.machinekit.io github: https://github.com/machinekit --- You received this message because you are subscribed to the Google Groups "Machinekit" group. To unsubscribe from this group and stop receiving emails from it, send an email to machinekit+unsubscr...@googlegroups.com. Visit this group at https://groups.google.com/group/machinekit. For more options, visit https://groups.google.com/d/optout.
