GS2961A Datasheet, PDF (62/104 Pages) Gennum Corporation – Ancillary data extraction

4.16 Video Signal Error Detection & Indication
The GS2961A includes a number of video signal error detection functions. These are
provided to enhance operation of the device when operating in SMPTE mode
(SMPTE_BYPASS = HIGH). These features are not available in the other operating modes
of the device (i.e. when SMPTE_BYPASS = LOW).
Signal errors that can be detected include:
1. TRS errors.
2. HD line based CRC errors.
3. EDH errors.
4. HD line number errors.
5. Video standard errors.
The device maintains an ERROR_STAT_X register. Each error condition has a specific
flag in the ERROR_STAT_X register, which is set HIGH whenever an error condition is
detected.
An ERROR_MASK register is also provided, allowing the user to select which error
conditions are reported. Each bit of the ERROR_MASK register corresponds to a unique
error type.
Each bit of each ERROR_MASK register corresponds to a unique error type.
By default (at power up or after system reset), all bits of the ERROR_MASK registers are
zero, enabling all errors to be reported. Individual error detection may be disabled by
setting the corresponding bit HIGH in the mask registers.
Error conditions are indicated by a DATA _ERROR signal, which are available for output
on the multifunction I/O output pins. This signal is normally HIGH, but is set LOW by the
device when an error condition has been detected.
This signal is a logical 'NOR' of the appropriate error status flags stored in the
ERROR_STAT_X register, which are gated by the bit settings in the ERROR_MASK
registers. When an error status bit is HIGH and the corresponding error mask bit is LOW,
the corresponding DATA_ERROR signal is set LOW by the device.
The ERROR_STAT_X registers, and correspondingly the DATA_ERROR signal, are
cleared at the start of the next video field or when read via the host interface, which ever
condition occurs first.
All bits of the ERROR_STAT_X registers are also cleared under any of the following
conditions:
1. LOCKED signal = LOW.
2. SMPTE_BYPASS = LOW.
3. When a change in video standard has been detected.
4. RESET_TRST = LOW
Table 4-13 shows the ERROR_STAT_X register and ERROR_MASK_X register.
NOTE: Since the error indication registers are cleared once per field, if an external host
micro is polling the error registers periodically, an error flag may be missed if it is
intermittent, and the polling frequency is less than the field rate.
GS2961A 3Gb/s, HD, SD SDI Integrated Receiver
Data Sheet
54385 - 2
September 2012
62 of 104