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2317 Rev 1.1 (17NOV04)
AuthenTec Confidential Information
58
7. Data Formats
7.1 Overview
The sensor communicates with the host via data packets. A one-byte
header that identifies the message precedes each data packet type. Note
that since the pixel data formats use all 8-bits per byte, the header bytes
are not unique in the data stream. Software can use the header bytes to
verify that it is synchronized with the data stream. They cannot be used as
a mechanism to synchronize with the data. If software gets out of synch
with the data, it should disable image scanning and issue a scan reset.
This will cause the data stream to stop. The following table shows the
header byte definitions for each message type.
Header
Byte
Definition
80h – BEh Register headers
BFh – DDh Reserved.
DEh
Precedes 32 byte histogram message.
DFh
Precedes eight byte authentication
value.
E0h
Precedes 500 ppi array data message in
gray scale. The array message is 192
columns x 16 pixels per column x ½ byte
per pixel = 1536 bytes. In 250 ppi mode,
the array message is 96 columns x 8
pixels per column x ½ byte per pixel =
384 bytes. In Extended Precision 250
ppi mode, the array message is 96
columns x 8 bytes per column = 768
bytes.
E1h-EFh Reserved
F0h
Precedes array data message in binary
mode. The array message is 192
columns x 16 pixels per column x 1/8
byte per pixel = 384 bytes. In 250 ppi
Mode, the array message is 96 columns
x 8 pixels per column x 1/8 byte per pixel
= 96 bytes.
F1h –FFh
Reserved.
Table 7-1
Command Byte Definition