SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
The NAND memory device provides a ready pin to indicate data availability after a block/page opening and to indicate that data programming is complete. The ready pin can be connected to one of the wait GPMC input pins; data read accesses must not be tried when the ready pin is sampled inactive (device is not ready) even if the associated chip-select WAITREADMONITORING bit field is set. The duration of the NAND device busy state after the block/page opening is so long (up to 50 micro second) that accesses occurring when the ready pin is sampled inactive can stall GPMC access and eventually cause a system time-out.
If a read access to a NAND flash is done using WAIT monitoring mode, the device is blocked during a page opening, and so is the GPMC. If the correct settings are used, other chip-selects can be used while the memory processes the page opening command.
To avoid a time-out caused by a block/page opening delay in NAND flash, disable the WAIT pin monitoring for read and write accesses (that is, set the GPMC_CONFIG1_i[21] WAITWRITEMONITORING and GPMC_CONFIG1_i[22] WAITREADMONITORING bits to 0, where i = 0 to 3), and use one of the following methods instead:
Even if the READWAITMONITORING bit is not set, the external memory nR/B pin status is captured in the programmed wait bit in the GPMC_STATUS register.
The READWAITMONITORING bit method must be used for other memories than NAND flash, if they require the use of a WAIT signal.