Rainbow Electronics AT77C105A - Manual (Page 27)

27
AT77C105A [Preliminary]
5419A–BIOM–01/05
Figure 13. Example of an 8-bit Access
During an 8-bit access, the sensor transmits two pixels (each pixel is coded on 4 bits).
Figure 14. Fast SPI Communication
Communication Speed The acquisition speed of the pixels is linked to the clock’s communication speed. The
faster the communication clock, the faster the authorized maximum finger sweeping
speed. The sensor supports fast communications up to 16 Mbps.
Reading of Frame A frame consists of 232 true columns and 1 dummy column of 8 pixels of 4 bits each. A
frame starts with a dummy column.
Figure 15. Example of a Frame
FSS/ = 0
Sending of Dummy Data
0b0000000
Reception of 2 Pixels
End of
Communication
?
Sending of 2 Pixels (8 Bits)
FSS/ = 1
No
Yes
Controller
Sensor
Bit2 Bit3
MSB Bit1 Bit0 Bit3 Bit2 Bit1 Bit0 Bit2 Bit1 Bit0 Bit3 Bit2 Bit1 Bit0 Bit3
MSB
SCK (Pixel Clock)
MISO
Transmission Clock
Edge (Sensor)
Reception Clock
Edge (Host)
Pixel 2i Pixel 2i - 1 Pixel 2i + 2 Pixel 2i + 1
p1
p2
p3
p4
p5
p6
p7
p8
0
F
0
F
2
0
0
0
Pixel Frame
P9
p10
p11
P12
P13
P14
P15
p16
Synchro = F0F00200
Dummy
Column
232 x 8 Pixels Column