GS9020 データシートの表示（PDF） - Unspecified

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GS9020

GENLINX ™II GS9020 Serial Digital Video Input Processor

Unspecified 

Sticky error flags that detect an error for a field remain

asserted until a HOSTIF read is performed on those error

flags. Sticky mode allows the user to perform HOSTIF reads

on the error flags to detect if any errors have occurred since

the last read, and are particularly useful when a read

cannot be performed after every field. When STICKY IN is

asserted HIGH, the incoming flags and validity bits are in

sticky mode. When STICKY OUT is asserted HIGH, the

outgoing flags and the EDH_CHKSM bit are in sticky mode.

Note that the INTERRUPT signal is derived from these

signals so that it too becomes sticky. STICKY IN and

STICKY OUT are available in the HOSTIF write table. The

ERROR FLAGS and the EDH_CHKSM bit are sticky HIGH.

That is, once they are set HIGH, they remain HIGH until a

read operation. The Validity bits are sticky LOW. That is,

once they are set LOW, they remain LOW until a read

operation.

In some applications, the user may wish to insert user

defined EDH error flags into the outgoing EDH packet. The

desired outgoing error flags are written into the OVERWRITE

VALUES words of the HOSTIF write table and are placed in

the outgoing EDH packet when the corresponding

OVERWRITE CONTROL bit is asserted HIGH. See Table 2

for the HOSTIF Write Table.

The GS9020 also allows the user to overwrite the seven

reserved words of the OUTGOING EDH packet. When

RO_CTRL (Reserved Word Overwrite Control) is asserted

HIGH, the GS9020 overwrites the reserved words in the

OUTGOING EDH packet with those specified in the HOSTIF

write table. If RO_CTRL is LOW, the GS9020 does not alter

the reserved words. RO_CTRL is a control bit in the HOSTIF

write table. The reserved words of the INCOMING EDH

packet are also available via the HOSTIF read table.

3.2 CRC Calculation And Updating

PIN

LOGIC OPR

HOST BIT

INCOMING FF CRC

OUTGOING FF CRC

INCOMING AP CRC

OUTGOING AP CRC

values based on the outgoing data stream are the ones

inserted into the data stream. As a result, the CRC values in

the outgoing data stream correctly reflect the contents of

the outgoing data stream.

The INCOMING FF and AP CRC values for the Full Field

(FF) and Active Picture (AP) regions can be read from the

HOSTIF read table. Similarly, the OUTGOING (calculated)

FF and AP CRC values for the Full Field and Active Picture

regions can be read from the HOSTIF read table.

3.3 Validity Bit

PIN

LOGIC OPR

HOST BIT

FFV

APV

The VALIDITY (V) bits (as per SMPTE 165) present in the

incoming EDH packet are used to indicate whether the CRC

values are valid or invalid. If the V bit is HIGH, the CRC

value is considered valid. In this case, the incoming CRC

value is compared with the calculated CRC value to identify

errors. If the V bit is LOW, the incoming CRC is invalid and a

CRC comparison is not performed. If the device receives an

EDH packet with the V bit set LOW it behaves as follows:

1. EDH = 0 (Not asserted for an invalid CRC)

2. EDA = EDAin "OR" EDHin (EDA calculated as usual)

3. A new calculated CRC value replaces the invalid one in

the output EDH packet

4. The V bit will be set HIGH in the output EDH packet

5. Depending on whether one or both or FFV or APV is low,

the Unknown Error Status (UES) flag corresponding to

either FF or AP or both, is set HIGH in the output data.

(No CRC check could be performed, so the data may or

may not contain errors).

The incoming V bits for the Full Field and Active Picture

regions are available in the HOSTIF read table as FFV and

APV, respectively. Outgoing full field (FFV) and active

picture (APV) validity bits are set HIGH unless explicitly

over-written through the HOSTIF write table or the flag port.

Since the device has the potential of modifying the full-field

and active picture data with features like ITU-R-601 clipping

and TRS insertion, the full field and active picture CRC

values must be calculated for both the incoming and

outgoing data streams. The calculated CRC values based

on the incoming data stream are used for comparison with

the embedded CRC values. However, the calculated CRC

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