Buffer Layout And Page Mapping For Small-Page Nand Flash Devices - Freescale Semiconductor MPC8313E Family Reference Manual

Enhanced Local Bus Controller
depending on the setting of ORn[PGS], with different buffers being accessible concurrently by software
and FCM.
To perform a page read operation from a NAND Flash device, software initializes the FCM command,
mode, and address registers, before issuing a special operation (FMR[OP] set non-zero) to a particular
FCM-controlled bank. FCM will execute the sequence of op-codes held in FIR, reading data from the
Flash device into the shared buffer RAM. While this read is taking place, software is free to access any
data stored in other, currently inactive buffers of the FCM buffer RAM through reads or writes to any bank
controlled by FCM. If command completion interrupts are enabled, an interrupt will be generated once
FCM has completed the read. When FCM has completed its last command, software can switch to the
newly read buffer and issue further commands.
To perform a page write operation, software first prepares data to be written in a fresh buffer. Then, the
FCM command, mode, and address registers are initialized, and a special operation (FMR[OP] set
non-zero) is issued to a particular FCM-controlled bank. FCM will execute the sequence of op-codes held
in FIR, writing data from shared buffer RAM to the Flash device. To ensure that the device is enabled for
programming, software must initialize FMR[OP] = 11, which prevents assertion of LFWP during the
write. While this write is taking place, software is free to access any data stored in other, currently inactive
buffers of the FCM buffer RAM through reads or writes to any bank controlled by FCM. When FCM has
completed its last command, software can re-use the previously written buffer and issue further
commands.
See Section 10.4.3.4.2, "Boot Block Loading into the FCM Buffer RAM," for a description of the shared
buffer RAM layout during boot.
10.4.3.1.1

Buffer Layout and Page Mapping for Small-Page NAND Flash Devices

The FCM buffer space is divided into eight 1-Kbyte buffers for small-page devices (ORn[PGS] = 0),
mapped as shown in Figure 10-46. Each page in a small-page NAND Flash comprises 528 bytes, where
512 bytes appear as main region data, and 16 bytes appear as spare region data. The EEPROM's page
numbered P is associated with buffer number (P mod 8), where P = FPAR[PI]. Since the bank size set by
ORn[AM] will be greater than 8 Kbytes, an identical image of the FCM buffer RAM appears replicated
every 8 Kbytes throughout the bank address space. It is recommended that the bank size be set to 32
Kbytes, which covers a single NAND Flash block for small-page devices.
For FCM commands, register FPAR sets the page address and, therefore, also the buffer number. In the
case that FBCR[BC] = 0, FCM transfers an entire page, comprising the 512-byte main region followed by
the 16-byte spare region; the 496-byte reserved region is not accessed, and remains undefined for software.
However, for commands given a specific byte count in FBCR[BC], FPAR[MS] locates the starting address
in either the main region (MS = 0) or the spare region (MS = 1). Where different eLBC banks control both
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