SLew rate Clock

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by namorada on Tue Jun 23 00:03:23 MST 2015

I'm trying to make an SPI connection with a slave. The master is, of course, the LPC18xx.
The SCK signal is populated on P1.19 (also tried on CLK0, but same result).
The PLL1 is configurated for 180MHz and clock the SSP1 module (used on SPI).

I try to make a connection to 15MHz SPI. When I look at the clock signal SCK, it is so rounded that it can work. After brief tests, it turns out I can not achieve SPI communication over 6Mhz.
I have initialized the pin like that :

Where :

#define SCU_MODE_HIGHSPEEDSLEW_EN  (0x1 << 5)/*!< Enable high-speed slew */
#define SCU_MODE_FUNC6             0x6/*!< Selects pin function 6 */

It is weird that the LPC18xx can get more 6Mhz but are not really too rounded ... Some among you have already encountered this problem ?

Thank you,