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RELEASED
PM73122 AAL1GATOR-32
DATASHEET
PMC-1981419
ISSUE 7
32 LINK CES/DBCES AAL1 SAR PROCESSOR
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
390
This disabling is required to prevent deactivation or reconfiguration in the middle
of a cell transfer.
Aside from the normal configurations, the block can also be placed in loopback
where cells received on the UI interface are transmitted back out onto the UI
interface. The block can be configured to loop all received cells by setting the
U2U_LOOP bit in the UI_COMN_CFG register. Alternately, only cells with a VCI
that matches the VCI contained in U2U_LOOP_VCI register can be looped back
while other cells proceed through normally. The VCI based UI to UI loopback
should be disabled when writing to U2U_LOOP_VCI.
14.3.1 VCI Loopback Setup Example in Multi-Address mode
Internal routing circuitry in Utopia-2 multi-address mode requires some special
consideration of the VCI values and select addresses. An example of a proper
configuration for VCI based loopback while in Utopia-2 multi-address mode is
shown in Figure 84. Note that cells sent to the sink interface address
TxAddr=bbb10 (where bbb is the configured base address) which have
VCI(15)=y and VCI(12:0)=z will be looped back because the resulting internal
VCI will match that in the U2U_LOOP_VCI register.
To maintain correct functionality, the cell’s VCI(14:13) should match that of the
lower bits of the select address TxAddr, ie, VCI(14:13)=10, and thus will appear
unchanged when exiting the source side. If Shift_VCI= 0 then all requirements
on VCI(14:13) are placed on VCI(10:9) instead.
All loopback cells will appear at the source side interface, regardless of the
setting of source configuration address (UI_SRC_CFG_ADR), but to maintain
symmetry the source configuration address should be set to RxAddr=bbb10 in
this example so that looped back cells appear on the same source address (Rx
slave) port as the sink address (Tx slave). An alternate setting would be to set
incoming VCI(14:13) = TxAddr(1:0) = RxAddr(1:0) = “00”, thus using the sink side
base address as the loopback address.