AT89LP51RC2 Atmel Corporation, AT89LP51RC2 Datasheet - Page 201

• Manufacturer Part Number: AT89LP51RC2
• Manufacturer: Atmel Corporation

Specifications of AT89LP51RC2

• Flash (kbytes): 32 Kbytes
• 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

24.5.2
24.5.2.1
3722A–MICRO–10/11
Bootloader Resources
Hardware Register
The Hardware condition PSEN = 0 during the deassertion of RST (falling edge for POL = 1, ris-
ing edge for POL = 0) forces the on-chip bootloader execution. This allows an application to be
built that will normally execute the end user’s code but can be manually forced into default Boot-
loader operation. As PSEN is a an output port in normal operating mode after reset, user
application should take care to release PSEN after the validating edge of the reset signal. The
hardware condition is sampled at the reset edge, and thus can be released at any time when the
reset input is inactive. To ensure correct microcontroller startup, the PSEN pin should not be tied
to ground during power-on (See
Figure 24-8. Hardware condition typical sequence during power-on (POL = 1)
The on-chip bootloader boot process is shown
Bootloader Process Description
Several on-chip resources are provided for use by the bootloader.
The hardware register of the AT89LP51RB2/RC2/IC2 is called the Hardware Byte or Hardware
Security Byte (HSB). It is a shadow of selected resources from the User Fuses and Hardware
Security Bits.
Table 24-13. Hardware Security Byte (HSB)
Hardware Condition
BLJB
SBV
X2
7
VCC
PSEN
RST
BLJB
6
AT89LP51RB2/RC2/IC2 Preliminary
5
-
Figure
Purpose
The Hardware Condition forces the bootloader execution whatever the
BLJB, BSB and SBV values.
The Boot Loader Jump Bit forces the application execution.
BLJB = 0 => Bootloader execution
BLJB = 1 => Application execution
The BLJB is a User configuration fuse. It can be modified by hardware
(programmer) or by software (API). Note: The BLJB test is performed by
hardware to prevent any program execution.
The Software Boot Vector contains the high address of customer
bootloader stored in the application.
SBV = FCh (default value) if no customer bootloader in user Flash.
Note: The customer bootloader is called by JMP [SBV]00h instruction.
24-8).
4
-
Figure 24-9 on page 203
XRAM
3
LB2
2
and described in
LB1
1
LB0
Table
0
201
.