XRT79L71_1 Datasheet, PDF (62/434 Pages) Exar Corporation – 1-CHANNEL DS3/E3 ATM UNI/PPP/CLEAR-CHANNEL FRAMER IC -

XRT79L71
1-CHANNEL DS3/E3 ATM UNI/PPP/CLEAR-CHANNEL FRAMER IC - REGISTER/MAP DESCRIPTION
REV. 1.0.0
BIT NUMBER
NAME
6
Multi-PHY Polling Enable
5
Back-to-Back Polling
Enable
4
Direct Status Indication
Enable
TYPE
R/W
R/W
R/W
DESCRIPTION
Multi-PHY Polling Enable:
This READ/WRITE bit-field permits the user to either enable or
disable Multi-PHY Polling for the Transmit UTOPIA Interface
block. If the user implements this feature (and configures the
XRT79L71 to operate in the Multi-PHY Mode) then the TxUClav
output pin will be driven (either "High" or "Low") based upon the
fill-status of the Transmit FIFO within the Channel that corre-
sponds to the Transmit UTOPIA Address that is currently being
applied to the TxUAddr[4:0] input pins.
If the user does not implement this feature (and then configures
the XRT79L71 to operate in the Single-PHY Mode), then the
TxUClav output pin will unconditionally reflect the Transmit FIFO
fill-status for Channel 0. No attention will be paid to the address
values placed upon the TxUAddr[4:0] input pins.
0 - Configures the Transmit UTOPIA Interface block to operate in
the Single-PHY Mode.
1 - Configures the Transmit UTOPIA Interface block to operate in
the Multi-PHY Mode.
Back-to-Back Polling Enable:
This READ/WRITE bit-field permits the user to configure the
Transmit UTOPIA Interface block to support Back-to-Back Poll-
ing.
Ordinarily, for Multi-PHY polling, the user is required to interleave
all UTOPIA Address values (that are to be placed on the TxU-
Addr[4:0] input pins) with the NULL Address (e.g., 0x1F). How-
ever, if the user configures the Transmit UTOPIA Interface block
to operate in the UTOPIA Level 3 Mode, and if the user also
enables Back-to-Back Polling, then the user does not need inter-
leave the UTOPIA Addresses with the NULL Address. In this
case, the user can simply apply a back-to-back stream of rele-
vant UTOPIA Addresses to the TxUAddr[4:0] input pins, and the
XRT79L71 will respond by driving the TxUClav output pins to the
appropriate states (depending upon the Transmit FIFO fill-sta-
tus).
0 - Disables Back-to-Back Polling. In this mode, the user must
interleave all UTOPIA Addresses (that are to be applied to the
TxUAddr[4:0] input pins) with the NULL Address.
1 - Enables Back-to-Back Polling. In this mode, the user does
not need to interleave all UTOPIA Addresses (that are to be
applied to the TxUAddr[4:0] input pins) with the NULL Address.
NOTE: In order to configure the Transmit UTOPIA Interface block
to operate in the Back-to-Back Polling Mode, the user
must also do the following.
a. Configure the Transmit UTOPIA Interface to operate in the
UTOPIA Level 3 Mode. This is accomplished by setting
Bit 7 (UTOPIA Level 3 Disable) within this Register to "0".
b. Configure the Transmit UTOPIA Interface to support Multi-
PHY Polling. This is accomplished by setting Bit 6 (Multi-
PHY Polling Enable) within this register to "1".
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