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MPC8349 maximum lbiu_clk frequency

Question asked by Etienne Alepins on May 24, 2019
Latest reply on May 27, 2019 by alexander.yakovlev



MPC8349AEC Rev. 13 "Hardware Specification" "Table 57. Operating Frequencies for TBGA" mentions that the maximum "Local bus frequency (LCLKn)" for a 533 MHz device is 133 MHz. However, LCLKn is obtained by a 1/2, 1/4 or 1/8 factor from lbiu_clk (also called lbc_clk). It is not possible to find in the documentation what is the maximum frequency of lbiu_clk (lbc_clk). Nothing in the documentation prevents setting lbiu_clk to 533 MHz by using RCWL[LBIUCM]=1 with a csb_clk of 266 MHz, while maintaining the local bus frequency to 133 MHz by using a LCRR[CLKDIV]=4.


If possible, what is the difference between the following two configurations? Will it increase performance?

1- 266 MHz csb_clk, 133 MHz local bus frequency, 266 MHz lbiu_clk

2- 266 MHz csb_clk, 133 MHz local bus frequency, 533 lMHz biu_clk