AT77C105A [Preliminary]
Communication Speed
To reduce consumption, the control interface’s communication speed is set to the lowest
possible speed and depends on the host’s configuration.
To communicate with “fast” controllers, the sensor’s communication speed can be set to
200 kbits/s.
Example for the MODECTRL
Register
Figure 10 represents a typical writing sequence into an internal register (MODECTRL
register in this example).
See Appendix B for flowchart.
Figure 10. Writing into an Internal Register
SSS
SCK
MOSI
0
x
0
x
1
x
1
x
0
x
0
x
0
x
0
x
1
x
0
x
0
x
0
x
0
x
1
x
x
x
x
x
MISO
Writing into MODECTRL Register Requested
New Data to be Written into MODECTRL Register
(Navigation and Click Mode)
Note:
The break on SCK on the SPI chronogram has been added for better comprehension only. In a real application, SCK can be
continuous.
Figure 11 represents a typical reading sequence of a register different from the naviga-
tion register. In this example, the status register is used.
Figure 11. Reading Sequence of a Register (Except for Navigation Registers)
SCK
MOSI
0
1
x
x
x
x
x
x
x
1
x
1
x
0
x
0
x
0
x
0
x
x
x
x
x
MISO
0
0
0
0
0
0
0
Reading of STATUS Register Requested
Emission of the STATUS Register
(Click Detected)
25
5419A–BIOM–01/05
ATMEL [ ATMEL ]
