Table A-2. 204 Data And Timing - Comtech EF Data SDM-2020 Installation And Operation Manual

Data Interfaces
Note: For proper operation, data and timing must be continuous, and meet the described criteria as
specified in Figure A-1, and Table A-2.
DATA Payload data is byte parallel, where DATA 7 is the most significant bit; or byte serial, where data is applied to
DATA 7 with the most significant bit preceding the least.
For 188 and 204 format, the payload is 187 bytes in length, preceded by a sync word. In the 204-byte mode, the
payload is followed by 16 bytes of reed-Solomon data, or 16 filler bytes.
CLOCK The clock is at the bit or byte rate in accordance with serial or parallel mode. The rising edge of the clock is
centered on the data.
SYNC SYNC timing depends upon the selection made for DVB FRAMING TYPE in the Configuration Interface menu
(refer to Figure 3-5).
DVB Framing Type
188 or 204
None
For the 188 or 204 byte framing modes, either a SYNC pulse or SYNC byte of value 47h is required, dependent
on the modulator configuration. Both may be applied, with only one having effect, dependent upon configuration.
When used, the SYNC pulse is active high centered over the SYNC word. In parallel operation, it is one byte
clock width. In serial operation, the modulator recognizes the SYNC pulse centered on the entire SYNC bit (8
clocks wide), or centered on the most significant bit of the byte (1 clock wide).
DVALID Although this signal is identified by both DVB and DBS formats, it is not used by the modulator.
A–4

Table A-2. 204 Data and Timing

The SYNC timing is derived from either the EXT SYNC or CORR ON
DATA selection from the Configuration Interface menu.
The SYNC signal is ignored.
SDM-2020 Satellite Demodulator
SYNC
Rev.3