GS9021 datasheet(9/26 Pages) GENNUM

9 / 26 page

521 - 65 - 05

If a mismatch occurs, the TRS_ERR signal is immediately

set HIGH and maintained HIGH until a correct TRS occurs.

The types of TRS errors detected are:

•TRS missing

•

TRS in wrong location

•

TRS-ID is different from the one generated by the

flywheel

The TRS_ERR signal is available via the HOSTIF read table.

TRS_ERR signal should only be considered valid if the

flywheel is enabled.

3. EDH PROCESSING BLOCK

This section describes the GS9021’s EDH features and

functionality.

3.1 Receive and Transmit Modes

In normal operation, the GS9021 is configured for one of

two modes, Receive (R/T = HIGH) or Transmit (R/T = LOW)

mode.

Transmit mode is appropriate for equipment which accepts

video that has no EDH packets or source equipment which

must generate a video stream with EDH. Receive mode is

appropriate for equipment where the input data already

contains EDH information. When the GS9021 is configured

in receive mode, the device expects to find an EDH packet

in the incoming data stream. The encoded CRC values in

the incoming data stream are compared with the calculated

CRC values as discussed in more detail below. Error flags

are set based on the results of these comparisons. If no

EDH packet is present, a new EDH packet is inserted (as in

transmit mode) but the UES flags are set to 1. In transmit

mode, no comparison is performed but a new EDH packet

is inserted with the calculated CRC values. All flags are set

to 0, unless set otherwise by the HOSTIF or flag port. See

Table 2 for the effect of the different settings of R/T and

CRC_MODE. Receive or Transmit mode is set via the R/T

control pin.

3.2 Error Flags

All 15 EDH error flags can be read from the HOSTIF read

table. The INCOMING ERROR FLAGS represent the EDH

error flags present in the incoming EDH packet. The

OUTGOING ERROR FLAGS represent the EDH error flags

present in the outgoing EDH packet (after modification by

the GS9021).

The INCOMING and OUTGOING ERROR FLAGS, the

incoming Validity bits (FFV and APV), and the EDH_CHKSM

bit can be made "sticky". 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. 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 3

for Host Interface WRITE table.

The GS9021 also allows the user to overwrite the 7 reserved

words of the OUTGOING EDH packet. When RO_CTRL

(Reserved Word Overwrite Control) is asserted HIGH, the

GS9021 overwrites the reserved words in the OUTGOING

EDH packet with those specified in the HOSTIF write table.

If RO_CTRL is LOW, the GS9021 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.

LOGIC OPR

HOST BIT

R/T

LOGIC OPR

HOST BIT

INCOMING ERROR FLAGS

OUTGOING ERROR FLAGS

STICKY IN

STICK OUT

OVERWRITE VALUES

OVERWRITE CONTROL

RO_CTRL

RESERVED WORDS (INCOMING)

RESERVED WORDS (OUTGOING)

GS9021 Datasheet(PDF) 9 Page - Gennum Corporation

GS9021 Datasheet(HTML) 9 Page - Gennum Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Datasheet Download

Link URL