Optional Features
Internal Clock Frequency The actual internal system clock can be the external clock divided by 1, 2, 4, or 8. If the
bit time length is (default configuration) 16 system clock pulses (see PS1, PS2 program-
mable bit timing registers), it is possible to have four different data rates by the pre-
scaler programming.
AT7908E Operational
Mode
The AT7908E device could be put on three different operational modes:
•
•
•
Functional Mode
Test mode
Power down mode
Functional Mode
Test Mode
This mode is the normal operational mode for the AT7908E device. The two input pins
test and sena must be put on logical value 0.
This mode is used by the chip manufacturer to test the AT7908E. The input pin test
must be logical value 1 and sena input pin could be logical values 0 or 1 according to
the execution of the scan chain test or not.
Power Down Mode
This mode could be used to put the AT7908E device on the sleep mode ( internal clock
is off). To put the AT7908E in this mode, the test input pin must be 0 and sena input pin
must be 1 .
24
AT7908E
4268D–AERO–11/09
ATMEL [ ATMEL ]
