C8051F336/7/8/9
13.1. Program Memory
The CIP-51 core has a 64 kB program memory space. The C8051F336/7/8/9 implements 16 kB of this pro-
gram memory space as in-system, re-programmable Flash memory, organized in a contiguous block from
addresses 0x0000 to 0x3DFF. The address 0x3DFF serves as the security lock byte for the device, and
addresses above 0x3DFF are reserved.
0x3FFF
Reserved Area
0x3E00
0x3DFF
0x3DFE
Lock Byte
Lock Byte Page
0x3C00
Flash Memory Space
0x0000
Figure 13.2. Flash Program Memory Map
13.1.1. MOVX Instruction and Program Memory
The MOVX instruction in an 8051 device is typically used to access external data memory. On the
C8051F336/7/8/9 devices, the MOVX instruction is normally used to read and write on-chip XRAM, but can
be re-configured to write and erase on-chip Flash memory space. MOVC instructions are always used to
read Flash memory, while MOVX write instructions are used to erase and write Flash. This Flash access
feature provides a mechanism for the C8051F336/7/8/9 to update program code and use the program
memory space for non-volatile data storage. Refer to Section “16. Flash Memory” on page 98 for further
details.
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