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
PIN
LOGIC OPR
HOST BIT
INCOMING ERROR FLAGS
OUTGOING ERROR FLAGS
STICKY IN
STICK OUT
GS9021A
OVERWRITE VALUES
OVERWRITE CONTROL
RO_CTRL
RESERVED WORDS (INCOMING)
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 GS9021A’s EDH features and
functionality.
3.1 Receive and Transmit Modes
RESERVED WORDS (OUTGOING)
PIN
R/T
LOGIC OPR
HOST BIT
In normal operation, the GS9021A 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 GS9021A 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
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 GS9021A 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 GS9021A overwrites the reserved words in the
OUTGOING EDH packet with those specified in the HOSTIF
write table. If RO_CTRL is LOW, the GS9021A 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.
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 GS9021A).
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GENNUM [ GENNUM CORPORATION ]
