Datasheet

16
7764A–8051–11/07
Figure 1. Low Pin Count regular boot process
Hardware condition: when the BSB is inactive, the only way to have the device run in ISP mode,
is to apply the hardware condition.
As the PSEN pin is not available in LPC packages, a port pin is used instead to apply the hard-
ware condition which consists by default to apply a hardware reset while pulling P1.0 pin to
ground then to release P1.0 pin once the hardware reset has been applied.
P1.0 is an Atmel default setting which can be easily changed by FLIP. The user can select a
another port if P1.0 is inappropriate for his application. Refer to the product’s bootloader
datasheet for further information.
RESET
BLJB = 1
P1_CF = FFh
P3_CF = FFh
P4_CF = FFh
P1_CF = P1
P3_CF = P3
P4_CF = P4
Start Bootloader
BSB = 0
SBV < 7Fh
Start User BootloaderStart Application
Yes
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
Yes
Yes
No
No
Hardware
Boot Process
Software Boot Process
in Low Pin Count
Bit ENBOOT in AUXR1 Register is
Initialized with BLJB Inverted
ENBOOT = 1
PC = F400h
ENBOOT = 0
PC = 0000h
Hardware condition
CAUTION
Do not change the BLJB bit