SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
NAND devices require multiple address programming phases. The software driver must issue the correct number of command and address program accesses, according to the device command set and the device address-mapping scheme.
NAND device-command and address-phase programming is achieved through write requests to the GPMC_NAND_COMMAND_i and GPMC_NAND_ADDRESS_i register locations (where i = 0 to 3) with the correct command and address values. These locations are mapped in the associated chip-select register region. The associated chip-select signal timing control must be programmed according to the NAND device timing specification.
Command and address values are not latched during the access and cannot be read back at the register location.
A write buffer is used to store write transaction information before the external device is accessed:
The GPMC_NAND_COMMAND_i and GPMC_NAND_ADDRESS_i registers (where i = 0 to 3) are 32-bit word locations, which means any 32-or 16-bit word access is split into 4- or 2-byte accesses if an 8-bit-wide NAND device is attached. For multiple-command phase or multiple-address phase, the software driver can use 32- or 16-bit word access to these registers, but it must consider the splitting and little-endian ordering scheme. When only one byte command or address phase is required, only byte write access to the GPMC_NAND_COMMAND_i and GPMC_NAND_ADDRESS_i registers can be used, and any of the four byte locations of the registers is valid.
The same applies to a GPMC_NAND_COMMAND_i and a GPMC_NAND_ADDRESS_i (where i = 0 to 3) 32-bit word write access to a 16-bit-wide NAND device (split into two 16-bit word accesses). In the case of a 16-bit word write access, the MSByte of the 16-bit word value must be set according to the NAND device requirement (usually 0). Either 16-bit word location or any one of the four byte locations of the registers is valid.