Table 68: Cgms Type B Readback Registers - Analog Devices ADV7850 Hardware Manual

Gemstar
The Gemstar decoded data is made available in the ancillary stream and through the fast I
of Gemstar can be made available VDP readback registers. Gemstar must be selected via
autodetection of the Gemstar standard between Gemstar 1x or Gemstar 2x formats, and decodes accordingly. This autodetection feature
must be enabled via the auto_detect_gem
configuration of the VDP. The type of decoded Gemstar can be found out by observing the
auto_detect_gem, Addr 48 (VDP), Address 0x61[4]
This control is used for the autodetection of the Gemstar type.
Function
auto_detect_gem
0
1 
vdp_status_gems_type, Addr 48 (VDP), Address 0x40[5] (Read Only)
This readback displays the Gemstar type.
Function
vdp_status_gems_type
0 
1
The Gemstar data that is available in the VDP readback register could be from any line of the input video on which Gemstar was decoded.
If the user wants to read the Gemstar data on a particular video line, the user should use the manual configuration described in
Section 10.1.2 and enable Gemstar decoding on only the required line.
PDC and UTC
PDC and UTC are data transmitted through teletext packet 8/30 format 2; and packet 8/30 format 1.
If PDC or UTC data is to be read through VDP readback registers, the corresponding teletext standard (WST – PAL System B) should be
decoded by VDP.
The whole teletext decoded packet is output on the ancillary data stream and the user can look for the magazine number, row number,
and 319designation code, and qualify the data as PDC/UTC.
If PDC/UTC packets are identified by the VDP, bytes 0 to 12 are updated to the vdp_gs_vps_pdc_utc_cgmstb_data registers (refer to
Table 68), and vdp_status_gems_vps is set accordingly. The full packet data is also available as ancillary data.
CGMS Type B
The CGMS Type B data can be present in 525p, 720p, and 1080i standards. The CGMS Type B standard has a total of 134 bits (16 bytes, 6
bits). The decoded data is made available in both the ancillary stream and in the VDP readback registers. The CGMS Type B data is made
available in VDP readback registers in a shared manner. The first four bytes are available in dedicated registers and the remaining bytes
are available in registers in the share registers of vdp_gs_vps_pdc_utc_cgmstb_data.
Rev. A May 2012
bit and program the decoder to decode Gemstar 2x on the required lines through manual
Description
Disable autodetection of Gemstar type
Enable autodetection of Gemstar type
Description
Gemstar 1X detected
Gemstar 2X detected

Table 68: CGMS Type B Readback Registers

CGMS Type B Readback Registers VDP Map
vdp_cgms_typeb_0
vdp_cgms_typeb_1
vdp_cgms_typeb_2
vdp_cgms_typeb_3
vdp_gs_vps_pdc_utc_cgmstb_data[7:0]
vdp_gs_vps_pdc_utc_cgmstb_data[15:8]
vdp_gs_vps_pdc_utc_cgmstb_data[23:16]
C port. For evaluation purposes only one line
2
gs_vps_pdc_utc_cgmstb[2:0].
vdp_status_gems_type
Address
0x3C
0x3D
0x3E
0x3F
0x47
0x48
0x49
319
ADV7850
VDP supports the
bit.