User guide

19–4 Chapter 19: Gamma Corrector MegaCore Function
Control Register Maps
Video and Image Processing Suite January 2013 Altera Corporation
User Guide
Control Register Maps
The Gamma Corrector can have up to three Avalon-MM slave interfaces. There is a
separate slave interface for each channel in parallel. Table 19–5 to Table 19–7 describe
the control register maps for these interfaces.
The control registers are read continuously during the operation of the MegaCore
function, so making a change to part of the Gamma look-up table during the
processing of a frame always has immediate effect. To synchronize changes to frame
boundaries, follow the procedure which is described in “Avalon-MM Slave
Interfaces” on page 3–17.
The width of each register in the Gamma Corrector control register map is always
equal to the value of the Bits per pixel per color plane parameter selected in the
parameter editor.
Table 19–5. Gamma Corrector Control Register Map: Interface 0
Address Register Name Description
0
Control
Bit 0 of this register is the Go bit, all other bits are unused. Setting this bit to 0
causes the Gamma Corrector MegaCore function to stop the next time control
information is read. Refer to “Avalon-MM Slave Interfaces” on page 3–17 for full
details.
1
Status
Bit 0 of this register is the Status bit, all other bits are unused. Refer to “Avalon-
MM Slave Interfaces” on page 3–17 for full details.
2 to 2
N
+1 where N
is the number of
bits per color plane.
Gamma Look-
Up Table
These registers contain a look-up table that is used to apply gamma correction to
video data. An input intensity value of x is gamma corrected by replacing it with the
contents of the (x+1)th entry in the look-up table. Changing the values of these
registers has an immediate effect on the behavior of the MegaCore function. To
ensure that gamma look-up values do not change during processing of a video
frame, use the
Go bit to stop the MegaCore function while the table is changed.
Table 19–6. Gamma Corrector Control Register Map: Interface 1
Address Register Name Description
0
Unused This register is not used
1
Unused This register is not used
2 to 2
N
+1 where N
is the number of
bits per color plane.
Gamma Look-
Up Table
These registers contain a look-up table that is used to apply gamma correction to
video data. An input intensity value of x is gamma corrected by replacing it with the
contents of the (x+1)th entry in the look-up table. Changing the values of these
registers has an immediate effect on the behavior of the MegaCore function. To
ensure that gamma look-up values do not change during processing of a video
frame, use the
Go bit in Interface 0 to stop the MegaCore function while the table is
changed.