PXN20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor 12-1
Chapter 12
Flash Memory Array and Control
12.1 Introduction
This section presents information about the following components on this device:
• The flash memory block
• The platform flash memory controller
The primary function of the flash memory module is to serve as electrically programmable and erasable
non-volatile memory. The NVM memory can be used for instruction and data storage. The block is a
non-volatile solid-state silicon memory device consisting of blocks of single-transistor storage elements,
an electrical means for selectively adding (programming) and removing (erasing) charge from these
elements, and a means of selectively sensing (reading) the charge stored in these elements. The flash is
addressable by word (32 bits) and page (128 bits).
The flash block is arranged as two functional units. The first functional unit is the flash core (FC). The FC
is composed of arrayed non-volatile storage elements, sense amplifiers, row selects, column selects, charge
pumps, and redundancy logic. The arrayed storage elements in the FC are sub-divided into physically
separate units referred to as blocks.
The second functional unit of the flash is the memory interface (MI). The MI contains the registers and
logic which control the operation of the FC. The MI is also the interface to the flash bus interface unit
(FBIU).
The flash core has three address spaces. The low-address space is 256 KB. The mid-address space is also
256 KB. The high-address space is 1.5 MB. The 256 KB of low memory is implemented using eight
16 KB blocks and two 64 KB blocks. The mid-address memory is implemented using two 128 KB blocks.
The high memory is implemented using three 512 KB blocks.
Figure 12-1
shows the segmentation for the flash on PXN20.
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