Si1000/1/2/3/4/5
13.2. Non-volatile Data Storage
The Flash memory can be used for non-volatile data storage as well as program code. This allows data
such as calibration coefficients to be calculated and stored at run time. Data is written using the MOVX
write instruction and read using the MOVC instruction. Note: MOVX read instructions always target XRAM.
An additional 1024-byte scratchpad is available for non-volatile data storage. It is accessible at addresses
0x0000 to 0x03FF when SFLE is set to 1. The scratchpad area cannot be used for code execution.
13.3. Security Options
The CIP-51 provides security options to protect the Flash memory from inadvertent modification by soft-
ware as well as to prevent the viewing of proprietary program code and constants. The Program Store
Write Enable (bit PSWE in register PSCTL) and the Program Store Erase Enable (bit PSEE in register
PSCTL) bits protect the Flash memory from accidental modification by software. PSWE must be explicitly
set to 1 before software can modify the Flash memory; both PSWE and PSEE must be set to 1 before soft-
ware can erase Flash memory. Additional security features prevent proprietary program code and data
constants from being read or altered across the C2 interface.
A Security Lock Byte located at the last byte of Flash user space offers protection of the Flash program
memory from access (reads, writes, or erases) by unprotected code or the C2 interface. The Flash security
mechanism allows the user to lock n 1024-byte Flash pages, starting at page 0 (addresses 0x0000 to
0x03FF), where n is the 1s complement number represented by the Security Lock Byte. Note that the
page containing the Flash Security Lock Byte is unlocked when no other Flash pages are locked
(all bits of the Lock Byte are 1) and locked when any other Flash pages are locked (any bit of the
Lock Byte is 0). See the Si1000 example below.
Security Lock Byte:
ones Complement:
Flash pages locked:
11111101b
00000010b
3 (First two Flash pages + Lock Byte Page)
Addresses locked:
0x0000 to 0x07FF (first two Flash pages) and
0xF800 to 0xFBFF (Lock Byte Page)
64KB Flash Device
(SFLE = 0)
32KB Flash Device
(SFLE = 0)
0xFFFF
0xFFFF
Reserved
0xFC00
Unpopulated
Address Space
(Reserved)
0xFBFF
Lock Byte
0xFBFE
Lock Byte Page
0xF800
Locked when
any other
Flash pages
0x8000
Flash
memory
organized in
1024-byte
pages
0x7FFF
Lock Byte
0x7FFE
are locked
Lock Byte Page
0x7C00
Unlocked Flash Pages
64/32KB Flash Device
Unlocked Flash Pages
(SFLE = 1)
Access limit
set according
to the Flash
security lock
byte
0x03FF
Scratchpad Area
(Data Only)
0x0000
0x0000
0x0000
Figure 13.1. Flash Program Memory Map
Rev. 1.0
143
SILICON [ SILICON ]
