AK8856 Datasheet, PDF (80/105 Pages) Asahi Kasei Microsystems – NTSC/PAL Digital Video Decoder

ASAHI KASEI
[ AK8856 ]
Variable Frame Rate Function
The AK8856 can vary the output frame rate. The frame rate can be selected by the [FRMRT1 : FRMRT0] bits of
Control 2 Register (R/W) [Sub Address0x04]
NTSC : 30 / 15 / 7.5 [fps]
PAL : 25 / 12.5 / 6.25 [fps]
Output timing is illustrated here. ( indicates “active”)
QVGA, CIF, QCIF, Rotated QVGA, Rotated CIF
Field
DVALID(ODEV 0,30fps)
DVALID(ODEV 1,30fps)
DVALID(ODEV 0,15fps)
DVALID(ODEV 1,15fps)
DVALID(ODEV 0,7.5fps)
DVALID(ODEV 1,7.5fps)
VGA,601
Field
DVALID(30fps)
DVALID(15fps)
DVALID(7.5fps
Note 1: These diagrams are typical for OFORM and OIF modes.
Note 2: When OIF [1:0] = 2’b 10 is set, VD pulse is not output at the default setting. However, HD pulse and DVALID signal
are output at the FIELD (Frame) where video is not output. In this case, the data is Black level data (Y : 0x10, Cb / Cr : 0x80).
In order to output VD pulse in this mode, set the VDPSUP-bit of Output Control 1 Register (R/W) [Sub Address 0x01].
Note 2: When OIF [1:0] = 2’b 10 is set, VD pulse is not output at the default setting. However, HD pulse and DVALID signal
are output at the FIELD (Frame) where video is not output. In this case, the data is Black level data (Y : 0x10, Cb / Cr : 0x80).
In order to output VD pulse in this mode, set VDPSUP-bit of Output Control 1 Register (R/W) [Sub Address 0x01].
Note 3: In VGA or 601 mode, ODEV setting does not affect output.
Note 4: When Vertical Sync is disturbed during switching signals., this timing may not be valid.
Setting of [VDPSUP-bit]
VDPSUP-bit condition
0
1
VD pulse output
To output VD pulse during Active Frames only.
To output VD pulse even at other than Active Frames.
Note
Rev-01
80
2007/03