AT697F datasheet(66/155 Pages) ATMEL

66 / 155 page

7703C–AERO–6/09

AT697F ADVANCE INFORMATION

If not programmed by software, the baud rate will be automatically be discovered. This is done

by searching for the shortest period between two falling edges of the received data (correspond-

ing to two bit periods). When three identical two-bit periods has been found, the corresponding

scaler reload value is latched into the reload register, and the DSUUC

BL bit is set . If the

DSUUC BL is reset by software, the baud rate discovery process is restarted. The baud-rate

discovey is also restarted when a ‘break’ is received by the receiver, allowing to change to

baudrate from the external transmitter. For proper baudrate detection, the value 0x55 should be

transmitted to the receiver after reset or after sending break.

The best scaler value for manually programming the baudrate can be calculated as follows:

scaler =

sdclk frequency x 10

baudrate x 8

Booting from DSU

By asserting DSUEN and DSUBRE at reset time, the processor will directly enter debug mode

without executing any instructions. The system can then be initialised from the communication

link, and applications can be downloaded and debugged. Additionally, external (flash) PROMs

for standalone booting can be re-programmed.

AT697F Datasheet(PDF) 66 Page - ATMEL Corporation