at89c5131 ATMEL Corporation, at89c5131 Datasheet - Page 38

• Manufacturer Part Number: at89c5131
• Description: 8-bit Flash Microcontroller With Full Speed Usb Device At89c5131
• Manufacturer: ATMEL Corporation

Default Values
Software Registers
4136C–USB–04/05
Table 38. Program Lock bits
Notes:
These security bits protect the code access through the parallel programming interface.
They are set by default to level 4. The code access through the ISP is still possible and
is controlled by the “software security bits” which are stored in the extra Flash memory
accessed by the ISP firmware.
To load a new application with the parallel programmer, a chip erase must be done first.
This will set the HSB in its inactive state and will erase the Flash memory. The part ref-
erence can always be read using Flash parallel programming modes.
The default value of the HSB provides parts ready to be programmed with ISP:
•
•
•
•
Several registers are used, in factory and by parallel programmers, to make copies of
hardware registers contents. These values are used by Atmel ISP (see Section “In-Sys-
tem Programming (ISP)”).
These registers are in the “Extra Flash Memory” part of the Flash memory. This block is
also called ”XAF” or eXtra Array Flash. They are accessed in the following ways:
•
•
•
Several software registers are described in Table 39.
Security level
BLJB: Cleared to force ISP operation.
X2: Set to force X1 mode (Standard Mode)
OSCON1-0: Set to start with 32 MHz oscillator configuration value.
LB2-0: Security level four to protect the code from a parallel access with maximum
security.
Commands issued by the parallel memory programmer.
Commands issued by the ISP software.
Calls of API issued by the application software.
1
2
3
4
1. U: unprogrammed or “one” level.
2. P: programmed or “zero” level.
3. X: don’t care
4. WARNING: Security level 2 and 3 should only be programmed after Flash and code
verification.
Program Lock Bits
LB0
U
P
X
X
LB1
U
U
P
X
LB2
U
U
U
P
Protection Description
No program lock features enabled.
MOVC instruction executed from external
program memory is disabled from fetching code
bytes from any internal memory, EA is sampled
and latched on reset, and further parallel
programming of the Flash and of the EEPROM
(boot and Xdata) is disabled. ISP and software
programming with API are still allowed.
Same as 2, also verify through parallel
programming interface is disabled and serial
programming ISP is disabled.
Same as 3, also external execution is disabled.
AT89C5131
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