SingMai Electronics
PT9 User Manual Revision 0.3
Page 20 of 38
9.
Register descriptions
Table 7 lists all of the control and status registers. All of the registers are 8 bit wide although some
are concatenated together to create longer words. Unused register bits read back as zeros.
Note that, if Control Register bit 7 is asserted (Auto register = ‘1’), then the default values for
NTSC-M, PAL, PAL-M and PAL-N will be used by the PT9 and only the Control registers and the
pre-emphasis register will be active.
The default values are shown in Table 8. The registers may still be written to and read from in Auto
register condition.
Please note that some registers can be set to values that are illegal and will produce invalid
outputs.
Asserting the RESETn input sets the PT9 to Auto register and Auto standard.
Register
Offset
Register Name
R/W
Bit Value
Description
$00
Control 1
R/W
Control Register
7
Auto register. When set to ‘1’ preset values are used for PT9
register values and only the two control registers andpre-
emphasis register may be programmed (PAL/NTSC/PAL-M/PAL-N
standards only). When this bit is set to ‘0’ the programmable
register values are used for PT9 control, allowing the PT9 to be
programmed for other standards or custom modes. (Default value
= ‘1’).
6
Auto standard. Selects whether the output standard is selected
manually ( = ‘0’) via Bit 5 or via the line standard detection of the
BT656 input (525 or 625 line) (= ‘1’). (Default value = ‘1’).
5
If bit 6 = ‘0’ this bit selects the output line standard.
4
Selects either PAL/NTSC output (= ‘0’) or PAL-N/PAL-M output (=
‘1’).
5:4
Line standard detect (bit 6 =
‘1’) or bit 5 (bit 6 = ‘0’)
Bit 4
0
0
NTSC-M (Default)
0
1
PAL-M
1
0
PAL
1
1
PAL-N
3-0
Not used
$01
Control 2
R/W
Control/status register
7:6
Not used.
Sinx/x enable
5
If ‘0’the sinx/x DAC compensation filter is turned off. If ‘1’ it is
turned on. Default is ‘1’.
Luma comb
enable
4
If ‘1’ the luma data is combed to reduce cross-colour in the video
decoder. If ‘0’ the luma comb filter is bypassed. (Default = ‘1’)
Chroma_off
3
Turns off the colour modulator if set to ‘1’ (forces monochrome
output). (Default = ‘0’)
VBI_Pass
2
If 0 the vertical blanking is from lines 623.5-23.5 and lines 311-335
for PAL and lines 1-20 and 263.5-283.5 for NTSC.
If 1 the vertical blanking is from lines 623.5-4.5 and 311-317 for PAL
and lines 1-9 and 263.5-272 for NTSC.
During the vertical VBI interval, lines 4.5-23.5 (9-20) and lines 317-
335 (272-283.5) data on the BT656 Y input is passed to the output
with a gain set by registers $2D and $2E. Data on the Cb and Cr
inputs is blanked. (Default = ‘0’).
Blackburst
1
If ‘0’ the BT656 input is used as the video data source. If ‘1’ the
output is blanked (burst/blanking output only).
Freerun
0
If ‘0’ the SPG timing is derived from the BT656 TRS codes (slave
mode) If ‘1’ the BT656 input is ignored and the Clock input is used
to derive all the synchronizing signals (master mode). When in
