The GPMC output clock generated for external synchronous memory or device is GPMC_CLKOUT.
- The GPMC_CLKOUT clock frequency is the GPMC_FCLK
functional clock frequency divided by 1, 2, 3, or 4, depending on the
GPMC_CONFIG1_i[1-0] GPMCFCLKDIVIDER bit field (where i = 0 to 3), with a
guaranteed 50-percent duty cycle. For information about the duty cycle error,
see the device-specific Datasheet.
- The GPMC_CLKOUT clock is activated only when the access in progress is defined as synchronous (read or write access).
- The GPMC_CONFIG1_i[26-25] CLKACTIVATIONTIME bit
field (where i = 0 to 3) defines the number of GPMC_FCLK cycles from start
access time to GPMC_CLKOUT activation.
- The GPMC_CLKOUT clock is stopped when cycle time completes and is asserted low between accesses.
- The GPMC_CLKOUT clock is kept low when access is defined as asynchronous.
CAUTION: When the cycle time completes, the GPMC_CLKOUT may
be high because of the GPMC_CONFIG1_i[1-0] GPMCFCLKDIVIDER bit field. To ensure
correct stoppage of the GPMC_CLKOUT clock within the required 50-percent duty
cycle, the user must extend the RDCYCLETIME or WRCYCLETIME value.
Note: To ensure a correct external clock cycle, the following rules must be applied:
- (RDCYCLETIME - CLKACTIVATIONTIME) must be a
multiple of (GPMCFCLKDIVIDER + 1).
- The PAGEBURSTACCESSTIME value must be a multiple of (GPMCFCLKDIVIDER + 1).