at89c5131 ATMEL Corporation, at89c5131 Datasheet - Page 37

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

Flash Registers and
Memory Map
Hardware Registers
Bootloader Jump Bit (BLJB)
Flash Memory Lock Bits
36
AT89C5131
The AT89C5131 Flash memory uses several registers:
•
•
The only hardware registers of the AT89C5131 is called Hardware Security Byte (HSB).
Table 37. Hardware Security Byte (HSB)
One bit of the HSB, the BLJB bit, is used to force the boot address:
•
•
The three lock bits provide different levels of protection for the on-chip code and data,
when programmed as shown in Table 38.
Number
Bit
5-4
2-0
Hardware registers can only be accessed through the parallel programming modes
which are handled by the parallel programmer.
Software registers are in a special page of the Flash memory which can be
accessed through the API or with the parallel programming modes. This page,
called “Extra Flash Memory”, is not in the internal Flash program memory
addressing space.
When this bit is set the boot address is 0000h.
When this bit is reset the boot address is F400h. By default, this bit is cleared and
the ISP is enabled.
X2
7
6
3
7
Mnemonic Description
OSCON1-0
LB2-0
BLJB
BLJB
Bit
X2
-
6
X2 Mode
Cleared to force X2 mode (6 clocks per instruction)
Set to force X1 mode, Standard Mode (Default).
Bootloader Jump Bit
Set this bit to start the user’s application on next reset at address 0000h.
Cleared this bit to start the bootloader at address F400h (default).
Oscillator Control Bits
These two bits are used to control the oscillator in order to reduce consummation.
OSCON
1
1
0
0
Reserved
User Memory Lock Bits
See Table 38
OSCON1
5
OSCON0
1
0
1
0
OSCON0
4
Description
The oscillator is configured to run from 0 to 32 MHz
The oscillator is configured to run from 0 to 16 MHz
The oscillator is configured to run from 0 to 8 MHz
This configuration shouldn’t be set
3
-
LB2
2
LB1
1
4136C–USB–04/05
LB0
0