C8051F124-GQR Datasheet, PDF (207/350 Pages) Silicon Laboratories – Mixed Signal ISP Flash MCU Family

C8051F120/1/2/3/4/5/6/7
C8051F130/1/2/3
15.2.1. Summary of Flash Security Options
There are three Flash access methods supported on the C8051F12x and C8051F13x devices; 1) Access-
ing Flash through the JTAG debug interface, 2) Accessing Flash from firmware residing below the Flash
Access Limit, and 3) Accessing Flash from firmware residing at or above the Flash Access Limit.
Accessing Flash through the JTAG debug interface:
1. The Read and Write/Erase Lock bytes (security bytes) provide security for Flash access
through the JTAG interface.
2. Any unlocked page may be read from, written to, or erased.
3. Locked pages cannot be read from, written to, or erased.
4. Reading the security bytes is always permitted.
5. Locking additional pages by writing to the security bytes is always permitted.
6. If the page containing the security bytes is unlocked, it can be directly erased. Doing so will
reset the security bytes and unlock all pages of Flash.
7. If the page containing the security bytes is locked, it cannot be directly erased. To unlock the
page containing the security bytes, a full JTAG device erase is required. A full JTAG
device erase will erase all Flash pages, including the page containing the security bytes and
the security bytes themselves.
8. The Reserved Area cannot be read from, written to, or erased at any time.
Accessing Flash from firmware residing below the Flash Access Limit:
1. The Read and Write/Erase Lock bytes (security bytes) do not restrict Flash access from user
firmware.
2. Any page of Flash except the page containing the security bytes may be read from, written to,
or erased.
3. The page containing the security bytes cannot be erased. Unlocking pages of Flash can
only be performed via the JTAG interface.
4. The page containing the security bytes may be read from or written to. Pages of Flash can be
locked from JTAG access by writing to the security bytes.
5. The Reserved Area cannot be read from, written to, or erased at any time.
Accessing Flash from firmware residing at or above the Flash Access Limit:
1. The Read and Write/Erase Lock bytes (security bytes) do not restrict Flash access from user
firmware.
2. Any page of Flash at or above the Flash Access Limit except the page containing the security
bytes may be read from, written to, or erased.
3. Any page of Flash below the Flash Access Limit cannot be read from, written to, or erased.
4. Code branches to locations below the Flash Access Limit are permitted.
5. The page containing the security bytes cannot be erased. Unlocking pages of Flash can
only be performed via the JTAG interface.
6. The page containing the security bytes may be read from or written to. Pages of Flash can be
locked from JTAG access by writing to the security bytes.
7. The Reserved Area cannot be read from, written to, or erased at any time.
Rev. 1.4
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