AT89LP51RB2 Atmel Corporation, AT89LP51RB2 Datasheet - Page 206

• Manufacturer Part Number: AT89LP51RB2
• Manufacturer: Atmel Corporation

Specifications of AT89LP51RB2

• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 42
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Adc Channels: 7
• Adc Resolution (bits): 10
• Adc Speed (ksps): 153.8
• Sram (kbytes): 1.375
• Self Program Memory: API
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 4
• Isp: SPI/OCD/UART
• Watchdog: Yes

24.5.3.2
24.5.4
24.5.4.1
206
AT89LP51RB2/RC2/IC2 Preliminary
Functional Description
Frame Description
Software Security Bits (SSB)
The Serial Protocol is based on the Intel Hex-type records.
Intel Hex records consist of ASCII characters used to represent hexadecimal values and are
summarized below.
Figure 24-10. Intel Hex Type Frame
The SSB protects any Flash access from Bootloader commands. The command "Program Soft-
ware Security Bit" can only write a higher priority level. There are three levels of security:
• Record Mark:
• Reclen:
• Load Offset:
• Record Type:
• Data/Info:
• Checksum:
• level 0: NO_SECURITY (FFh)
• level 1: WRITE_SECURITY (FEh)
• level 2: RD_WR_SECURITY (FCh)
Record Mark is the start of frame. This field must contain ’:’.
Reclen specifies the number of bytes of information or data which follows the Record Type
field of the record.
Load Offset specifies the 16-bit starting load offset of the data bytes, therefore this field is
used only for Data Program Record (see Section “Bootloader Command Summary”).
Record Type specifies the command type. This field is used to interpret the remaining
information within the frame. The encoding for all the current record types is described in
Section “Bootloader Command Summary”.
Data/Info is a variable length field. It consists of zero or more bytes encoded as pairs of
hexadecimal digits. The meaning of data depends on the Record Type.
The two’s complement of the 8-bit bytes that result from converting each pair of ASCII
hexadecimal digits to one byte of binary, and including the Reclen field to and including the
last byte of the Data/Info field. Therefore, the sum of all the ASCII pairs in a record after
converting to binary, from the Reclen field to and including the Checksum field, is zero.
This is the default level.From level 0, one can write level 1 or level 2.
For this level it is impossible to write in the Flash memory, BSB or SBV. The Bootloader
returns ’P’ on write access. From level 1, one can write only level 2.
Level 2 forbids all read and write accesses to/from the Flash memory. The Bootloader returns
’L’ on read or write access. Only a full chip erase in parallel mode (using a programmer) or
ISP command can reset the software security bits. From level 2, one cannot read and write
anything.
Record
1-byte
Mark
’:’
Reclen
1-byte
2-bytes
Load
Offset
1-byte
Record
Type
n-bytes
Data
Info
or
Checksum
1-byte
3722A–MICRO–10/11