Rainbow-electronics AT77C104B Bedienungsanleitung PDF herunterladen (Seite 26)

AT77C104B

5347B–BIOM–08/04

Figure 16. Reading of Frame

Notes: 1. For the first array or frame reading, 40 dummy clock cycles must be sent before the first data arrives. This is necessary for

the initialization of the chip pipeline. Consequently, the first synchronization sequences appear after 40 clock cycles. For the

following array readings, data arrives at each clock cycle. One should implement a synchronization routine in the protocol to

look for the F0F00200 pattern.

2. The Most Significant Bit (MSB) is sent first.

Reading of Entire Image The FingerChip delivers fingerprint slices or frames with a height of 0.4 mm and a width

of 11.6 mm (this equals 8 × 232 pixels). Pixels are sampled/read sequentially and are

synchronous with SCK. Raw slices are captured by the acquisition system and over-

lapped with the corresponding X or Y finger displacement computed by Atmel

reconstruction software. This reconstruction software supports a sweeping speed from 2

to 20 cm/s.

The table below shows finger speeds according to the different clock frequencies. The

reconstruction results are obtained after acquisition of all slices.

SCK

MISO

Dummy Column

F 0 F 0 20 0 P2 P1 P4 P6 P3 P5 P8 P7

First Pixel

Column

0 P10 P9

Second Pixel

Column

Table 14. Finger Speeds Versus Clock Frequencies

Fsck

(MHz)

Data Rate

(Mbit/s)

Slice Rate

(Slices/s)

Absolute

Maximum Finger

Speed (cm/s) Comments

1 1 134 3 Too slow

2 2 268 6 Too slow

4 4 536 12 Minimum

6 6 804 18 Normal speed

8 8 1072 24 Good speed

12 12 1608 36 Very good speed

16 16 2146 48 Very good speed

1 2 ... 21 22 23 24 25 26 27 28 29 30 31 ... 35 36

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Rainbow-electronics AT77C104B Bedienungsanleitung Seite 26