I’m porting our ARM development system from the STR-710EVAL board to the Olimex STR-P711 board. I’m trying to program the PLL for 48 MHz MCLK and 24 MHz PCLK1,2. This worked just fine on the STR-710EVAL (which has a 16 MHz CK input) with the following register settings:
MDIVR 0000
PDIVR 0101
PLL1CR 0051
CFR 8009
Now I’m using these values for the STR-P711 (4 MHz CK input):
MDIVR 0000
PDIVR 0101
PLL1CR 0050
CFR 0009
The LOCK bit in CFR never goes true. What have I overlooked?