GPMC_CLK is the external clock provided to the attached synchronous memory or device.
- The GPMC_CLK 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 7), with a guaranteed 50-percent duty cycle. For information about the duty cycle error, see the device data manual.
- The GPMC_CLK 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 7) defines the number of GPMC_FCLK cycles from start access time to GPMC_CLK activation.
- The GPMC_CLK clock is stopped when cycle time completes and is asserted low between accesses.
- The GPMC_CLK clock is kept low when access is defined as asynchronous.
CAUTION: When the cycle time completes, the GPMC_CLK may be high because of the GPMCFCLKDIVIDER bit field. To ensure correct stoppage of the GPMC_CLK 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).