Underclocking SDRAM

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by MindBender on Wed Jul 15 05:58:16 MST 2015
The Embedded Artists LPC1788 board uses an IS42S32800B-7BL SDRAM chip, which is 256Mbit (8Mx32) in size and specifies a clock rate of 143MHz. However, the demo software that comes with the board sets CCLKSEL to 0x00000101 and EMCCLKSEL to 0x00000001, operating this SDRAM chip at 60MHz.

Is it safe/reliable to underclock SDRAM (that far)? If so, do we need to alter latencies to make sure it is still refreshed in time?

We found the IS42S32800B-7BL a bit too big/expensive for our own design, so we have found an alternative, but that one too is rated well over 60MHz.