
TMC22x5yA
PRODUCT SPECIFICATION
52
For PAL comb filters the 
LYE
, 
LME
, and 
LPE
 errors signals 
are always selected by default. In this way the error signals 
into the XLUT always represent the comb filter being imple-
mented. The resolution of the error signals selected is con-
trolled by the XIP[1:0] register bits as shown in Table 6: 
XLUT Input Selection. The position of these error signals on 
the XLUT input address X[7:0] is also shown. 
The selected comb fail signals are translated by the user-
programmed configuration within the 256*5 XLUT into the 
mix signal (K) which controls the 30 levels of cross-fade 
between the weighted comb filter and the band split filters. 
The 1 to 31 mix signal is modified on the input to the cross-
fade to produce a 0 to 32 control signal, as shown in Table 7.
The special function assigned to K = 0 is programmed into 
the XSF[1:0] register bits, as shown in Table 8.
Table 8. XLUT Special Function Definitions
The “Flat with notch” selection passes the 
FLAT
input 
through onto the luminance channel and selects the notch 
filter, centered at 0.25 of the normalized clock frequency. 
This mode is therefore only useful with inputs at 4*Fsc or in 
cases when a notch at 0.25 of the normalized clock 
frequency is adequate for application.
The XLUT output, is fed through a bypassable low-pass 
filter KLPF to avoid switching between comb and simple 
decoders on a pixel by pixel basis. When the special function 
is selected (K = 0) the input to the KLPF is held and the filter 
is automatically bypassed. The output of the XLUT can be 
externally monitored by reading XOP[4:0] in register 4Bh.
Table 6. XLUT Input Selection 
XIP[1:0]
00
Function
2 bits of phase error (X[7:6]), 3 bits of 
chroma (X[5:3]) and luma magnitude error 
(X[3:0]).
4 bits of chroma (X[7:4]) and luma 
magnitude error (X[3:0]).
3 bits of phase error (X[7:5]), 3 bits of 
chroma magnitude error (X[4:2]), and 2 
bits of luma magnitude error (X[1:0]).
4 bits of phase error (X[7:4]) and chroma 
magnitude error (X[3:0]).
01
10
11
Table 7. XLUT Output Function. 
XLUT 
OUTPUT
0
K
Special function (e.g. luma comb and HPF 
on chroma)
0 - 100% Bandsplit
2
3
:
1
2
3
:
16
:
29 
30
31
16 - 50% Bandsplit, 50% Comb
:
29
30
32 - 100% Comb
KIP
1-0
XLUT special function selection
Y
comb
simple
flat with notch
flat with notch
C
00
01
10
11
simple
comb
simple
comb
Table 7. XLUT Output Function. 
(cont.)
XLUT 
OUTPUT
K
Figure 20. XLUT Input Selection 
XLUT
XLUT
Input
Select
Filter
2:1
MUX
65-22x5y-61
K[4:0]
XFEN
XIP[1:0]
X[7:0]
YERR
PERR
MERR