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Gpdata_buffer, Little endian vs. big endian byte order, R in chapter – ALLIED Vision Technologies Oscar F-810 User Manual

Page 201: E chapter

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Configuration of the camera

OSCAR Technical Manual V2.4.0

201

GPDATA_BUFFER

GPDATA_BUFFER is a general purpose register that regulates the exchange of
data between camera and host for:

writing look-up tables (LUTs) into the camera

uploading/downloading of the shading image

GPDATA_INFO

Buffer size query

GPDATA_BUFFER

indicates the actual storage range

Little endian vs. big endian byte order

Read/WriteBlock accesses to GPDATA_BUFFER are recommended, to read
or write more than 4 byte data. This increases the transfer speed com-
pared to accessing every single quadlet.

The big endian byte order of the 1394 bus is unlike the little endian
byte order of common operating systems (Intel PC). Each quadlet of the
local buffer, containing the LUT data or shading image for instance, has
to be swapped bytewise from little endian byte order to big endian byte
order before writing on the bus.

Register

Name

Field

Bit

Description

0xF1000FFC GPDATA_INFO

---

[0..15]

Reserved

BufferSize

[16..31]

Size of GPDATA_BUFFER
(byte)

0xF1001000

0xF10017FC

GPDATA_BUFFER

Table 105: Advanced register: GPData buffer

Note

L

Read the BufferSize before using.

GPDATA_BUFFER can be used by only one function at a
time.

Bit depth

little endian

big endian

Description

8 bit

L0 L1 L2 L3

L3 L2 L1 L0

L: low byte

H: high byte

16 bit

L0 H0 L1 H1

H1 L1 H0 L0

Table 106: Swapped first quadlet at address offset 0

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