DS92UT16TUF Datasheet, PDF (30/86 Pages) National Semiconductor (TI) – UTOPIA-LVDS Bridge for 1.6 Gbps Bi-directional Data Transfers

16.0 Embedded Communication
Channel Operation
This section describes the ECC operation. The ECC trans-
mits one 8 byte message per frame over the link under
software control. Flow control ensures that messages are
not overwritten at the receive end.
The message to be transmitted is written to the
ETXD7–EXTD0 transmit buffer registers and the received
messages are stored in the Port A ERAD7–ERAD0 or Port B
ERBD7–ERBD0 receive buffer registers. Software control is
achieved on the transmit side using the ECC Transmit Buffer
Ready (ETXBR) interrupt of the ETXRXA register and the
ECC Transmit Send (ETXSD) register.
There are independent receive sections in Port A and Port B
and these are controlled using the ECC Receive Port A
Buffer Full (ERABF) interrupt of the Receive Port A Local
Alarm (RALA) register, and the ECC Receive Port B Buffer
Full (ERBBF) interrupt of the Receive Port B Local Alarm
(RBLA) register respectively. The choice of receiving ECC
messages on Port A or Port B is controlled by the ECCB and
ECCA bits of the Link Status and Control (LKSC) register.
The Remote Alarm and Signalling Byte carries the ECC
signaling bits. The transmitted Remote Alarm and Signalling
Byte carries the ESS signal for both of the local ECC receive
sections, ESSA and ESSB. At the receiver a choice must be
made as to which ESS bit of the received Remote Alarm and
Signalling Byte is valid for the local ECC transmitter. This is
controlled by the RAESS and RBESS bits of the RACTL and
RBCTL registers respectively.
FIGURE 15. The Basic Structure Of The ECC
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16.1 BASIC ECC PROTOCOL — ONE TRANSMIT AND
ONE RECEIVE
The basic operation of an ECC link is described here using
the transmit section of the device at one end of the LVDS link
and a single receive section (Port A) of the device at the
other end of the link.
The ECC transmitter and receiver communicate via the em-
bedded control signals EVN, ESSA and ESSB in the Remote
Alarm and Signalling byte contained in the F1 byte of TC6.
By default both receive ports will extract the incoming ESSA
bit as the valid ESS to pass to the ECC transmit section. This
assumes that the local ECC transmit section is connected to
the remote device receiver port A. If the local transmitter is
connected to the remote device receiver port B then the
incoming ESSB bit must be selected as the valid ESS to
pass to the local ECC transmit section. The selection of valid
incoming ESS bit is accomplished using the RAESS and
RBESS bits of the RACTL and RBCTL registers respectively.
Note that only one of the incoming remote ESS bits is valid
on each link as the local transmitter cannot be connected to
both receivers on another DS92UT16 device.
The EVN and ESS bits are interpreted as follows:
EVN - Set = Valid ECC data in F1/F2 bytes of TC13, TC20,
TC41 and TC48.
Clear = Null (not valid) ECC data in F1/F2 bytes of
TC13, TC20, TC41 and TC48.
ESS - Set = Stop sending ECC data as receive buffer is full.
Clear = Send ECC data as receive buffer is ready.
The protocol for transmission of an ECC message is as
follows.
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