ST
ST
ST
SP
SP
ST
ET
ET
ET
ET
PH
PH
PF
PF
Data
Data
ULPM
ULPM
ULPM
Long
packet
Long
packet
Short
packet
Short
packet
Key:
ST: Start of transmission
ET: End of transmission
PH: Packet header
PF: Packet footer
ULPM: Ultra-low power mode
SP: Short packet
camisp-241
camisp-242
DataID
Shortpacket
datafield
ECC
32-bit short packet (SP)
Data type (DT) = 0x00 – 0x0F
Public Version
Camera ISP Environment
www.ti.com
Figure 6-22. Camera ISP CSI2 Protocol Layer With Short and Long Packets
Two packets are always separated from each other with a sequence of a ULPM, an ET, and an ST.
6.2.4.5.2.1 Camera ISP CSI2 Short Packet
A short packet is identified by data types 0x00 to 0x0F. A short packet can be used for frame or line
synchronization or for generic data.
shows the structure of a short packet.
Figure 6-23. Camera ISP CSI2 Short Packet Structure
For frame-synchronization data types, the short packet data field is the frame number. For
line-synchronization data types, the short packet data field is the line number. For generic short packet
data types, the content of the short packet data field is user-defined.
The 16-bit frame number, when used, is always nonzero to distinguish it from the use case where the
frame number is inoperative and remains set to 0. The behavior of the 16-bit frame number is one of the
following:
•
The frame number is always 0. The frame number is inoperative.
•
The frame number increments by 1 for every FS packet with the same virtual channel and is
periodically reset to 1 (1, 2, 1, 2, 1, 2, 1, 2 or 1, 2, 3, 4, 1, 2, 3, 4).
For line-start code (LSC) and line-end code (LEC) synchronization packets, the short packet data field
contains a 16-bit line number. This line number is the same for the LS and LE packets corresponding to a
given line. Line numbers are logical line numbers and do not necessarily equal physical line numbers. The
16-bit line number, when used, is always nonzero to distinguish it from the case where the line number is
inoperative and remains set to 0.
The behavior of the 16-bit line number is one of the following:
•
The line number is always 0. The line number is inoperative.
•
The line number increments by one for every LS packet within the same virtual channel and the same
data type. The line number is periodically reset to 1 for the first LS packet after an FS packet. The
intended usage is for progressive scan (non-interlaced) video data streams. The line number must be
a nonzero value.
•
The line number increments by the same arbitrary step value greater than one for every LS packet
within the same virtual channel and the same data type. The line number is periodically reset to a
nonzero arbitrary start value for the first LS packet after an FS packet. The arbitrary start value can be
1114
Camera Image Signal Processor
SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated