We are running the LPC4076 at 120MHz with Power Boost ON. The User Manual UM10562 rev 3 12 March 2014 states that the FLASHTIM value should be binary 0100: "Flash accesses use 5 CPU clocks. Use for up to 100 MHz CPU clock with power boost off (see Section 3.12.6). Use this setting for operation from 100 to 120 MHz operation with power boost on."
In the MCUXpresso Peripherals window, it says one of the possible values is "FLASH_ACCESSES_USE_4 (0x3) - Flash accesses use 4 CPU clocks. Use for up to 80 MHz CPU clock with power boost off. Use this setting for operation from 100 to 120 MHz operation with power boost on."
File sysctl_17xx_40xx.h has this enumerated list which agrees with MCUXpresso:
/**
* @brief FLASH Access time definitions
*/
typedef enum {
FLASHTIM_20MHZ_CPU = 0, /*!< Flash accesses use 1 CPU clocks. Use for up to 20 MHz CPU clock */
FLASHTIM_40MHZ_CPU = 1, /*!< Flash accesses use 2 CPU clocks. Use for up to 40 MHz CPU clock */
FLASHTIM_60MHZ_CPU = 2, /*!< Flash accesses use 3 CPU clocks. Use for up to 60 MHz CPU clock */
FLASHTIM_80MHZ_CPU = 3, /*!< Flash accesses use 4 CPU clocks. Use for up to 80 MHz CPU clock */
FLASHTIM_100MHZ_CPU = 4, /*!< Flash accesses use 5 CPU clocks. Use for up to 100 MHz CPU clock */
#if defined(CHIP_LPC177X_8X) || defined(CHIP_LPC40XX)
FLASHTIM_120MHZ_CPU = 3, /*!< Flash accesses use 4 CPU clocks. Use for up to 120 MHz CPU clock with power boot on*/
#else
FLASHTIM_120MHZ_CPU = 4, /*!< Flash accesses use 5 CPU clocks. Use for up to 120 Mhz for LPC1759 and LPC1769 only.*/
#endif
FLASHTIM_SAFE_SETTING = 5, /*!< Flash accesses use 6 CPU clocks. Safe setting for any allowed conditions */
} FMC_FLASHTIM_T;
On power up the part defaults to the latter value matching MCUXpresso, but I suspect that the longer delay specified in the User Manual is correct. Which value should we use at 120MHz?
Thanks,
Doug
