DS92UT16 datasheet(21/111 Pages) TI1

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DS92UT16

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SNOS992E – JANUARY 2002 – REVISED APRIL 2013

ATM Polling

When configured as an ATM Layer device, the DS92UT16 polls the connected PHY ports using the MPhy

address busses U_TxAddr and U_RxAddr. Only those ports which are connected will be polled. The connected

ports list defined in the UCPL3–UCPL0 registers is used to determine which ports are connected. The PHY ports

respond on U_TxCLAV[7:0] and U_RxCLAV[7:0]. The MPhy address determines the Port and the CLAV pin

number determines the sub-port. Therefore up to 8 sub-ports may be connected to a port. Polling of a single

MPhy address will get eight responses on the eight CLAV lines. The DS92UT16 uses the connected sub-port list

defined in the UCSPL register to determine which of these eight sub-port responses are valid. On reset, the

UCPL3–UCPL0 registers are all set to 0xFF and the UCSPL register is set to 0x01, so the DS92UT16 will poll all

ports and assume only sub-port zero is connected.

PHY Polling

When configured as a PHY Layer device, the DS92UT16 is polled by the connected ATM device. During polling,

the DS92UT16 will only respond to MPhy addresses on U_TxAddr and U_RxAddr, which are defined as

connected. The connected ports list defined in the UCPL3–UCPL0 registers is used to determine which ports are

connected. On reset the UCPL3–UCPL0 registers are all set to 0xFF so the DS92UT16 will respond to all MPhy

addresses during polling.

NOTE

There must always be at least one connected port defined in the UCPL3–UCPL0

registers. If no ports are to be connected then use Configuration Traffic Inhibit mode

described in Configuration and Traffic Inhibit Operation.

Sub-Port Address

The operation of the sub-port address is illustrated in Figure 10. To use the Extended Level 2 mode that allows

addressing up to 248 Ports, the ATM Layer (that which drives the DS92UT16 in PHY mode) must be capable of

inserting a three bit sub-port address in the PDU cell for use by the DS92UT16. This 3-bit sub-port address must

reside in either the User Prepend, Cell Header, or UDF bytes. It’s location is defined in the UTOPIA Sub-Port

Address Location (USPAL) and UTOPIA Sub-Port Address Mask (USPAM) registers. The USPAL register

defines which byte of the User Prepend, Cell Header, or UDF, contains the address and the USPAM register

defines which three bits of that byte are the sub-port address.

Transmit Path Example: The MPhy address is interpreted as the Port address. So, a cell destined for the PHY

designated as Port 0 Sub-Port 7 has the three bit sub-port address 7 (binary “111”) inserted into the defined sub-

port address location of the PDU cell by the ATM layer head-end. It is then transmitted to the DS92UT16 in PHY

mode using MPhy address 0. The DS92UT16 in PHY mode does not examine the sub-port address because all

cells are transmitted down-bridge anyway.

At the far end, the DS92UT16 in ATM mode extracts the sub-port address. This is used to determine which sub-

port CLAV/ENB signals the destination PHY is connected to. A port address of 0 and a sub-port address of 7

means that the destination PHY is MPhy address 0 attached to U_TxENB[7] and U_TxCLAV[7]. The cell is then

transmitted to that PHY.

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