Vdp Decoded Data Readback Registers; Teletext Readback Registers; Cgms And Wss Readback Registers - Analog Devices ADV7850 Hardware Manual

Function
vdp_ttxt_type_man_en
0 
1
vdp_ttxt_type[1:0], Addr 48 (VDP), Address 0x60[1:0]
This readback indicates the teletext type detected. It is functional only if vdp_ttxt_type_man_en is set to 1.
Function
vdp_ttxt_type[1:0]
00 
01
10
11
10.3

VDP DECODED DATA READBACK REGISTERS

Teletext Readback Registers

10.3.1
Since teletext is a high data rate standard, decoded bytes are provided via ancillary data. A status bit is provided to indicate the teletext
detection status.
vdp_status_ttxt, Addr 48 (VDP), Address 0x40[7] (Read Only)
This readback displays the teletext detection status.
Function
vdp_status_ttxt
0 
1

CGMS and WSS Readback Registers

10.3.2
CGMS and WSS convey the same type of information for different video standards. WSS is a 625i standard while CGMS is a 525i, 525p,
625p, 720p, and 1080i standard. Hence, the CGMS and WSS readback registers are shared. WSS is biphase coded and the VDP does a
biphase decoding to produce the 14 raw WSS bits to be available in the CGMS and WSS VDP readback registers. A status bit is set when
this data is available.
status_clear_wss_cgms, Addr 48 (VDP), Address 0x78[2] (Self-Clearing)
This control is used to refresh the WSS and CGMS readback registers. This is a self-clearing bit.
Function
status_clear_wss_cgms
0 
1
vdp_status_wss_cgms, Addr 48 (VDP), Address 0x40[2] (Read Only)
This readback displays the WSS or CGMS type A data detection status.
Rev. A May 2012
Description
Manual programming of teletext disabled
Manual programming of teletext enabled
Description
ITU_BT.653-625/50-A - for PAL
ITU_BT.653-625/50-B(WST) - for PAL; ITU_BT.653-525/60-B - for NTSC
ITU_BT.653-625/50-C(WST) - for PAL; ITU_BT.653-525/60-C or EIA516(NABTS) - for NTSC
ITU_BT.653-625/50-D - for PAL; ITU_BT.653-525/60-D -
Description
Teletext not detected
Teletext detected
Description
Do not refresh WSS and CGMS readback registers
Refresh WSS and CGMS readback registers
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ADV7850