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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
407
15.2 Sink Utopia
In ATM master mode, the SNK_INTF block receives RATM_DATA, RATM_PAR,
RATM_SOC, and RATM_CLAV while driving RATM_ENB. During reset the
SNK_INTF tristates the RATM_ENB (and all other SRC_INTF outputs). After the
end of reset and after UI_EN in the UI_COMN_CFG register is set, if the
RATM_CLAV input signal is not asserted the SNK_INTF waits and RATM_ENB
is deasserted high. As shown in Figure 101, once the RATM_CLAV input signal
is asserted, the RATM_RENB output signal is asserted low 2 cycles later and it is
expected that the PHY slave will deliver the first data byte one cycle after RENB
goes low. Typically a start-of-cell signal will be sent by the PHY slave along with
the first byte of data, however RATM_SOC is optional and the RATM_SOC input
could be tied low. Note however, not using an SOC eliminates the possibility of
runt cell detection. Once RATM_ENB goes low, a counter is started, and 53
bytes are expected. If an SOC occurs within a cell, the counter reinitializes and
the previous corrupted cell will be dropped and the second good cell will be
received. The SNK_INTF block stores the ATM cell in the receive FIFO. The 4
cell MCFF FIFO allows the interface to accept data at the maximum rate and if
the FIFO fills, the RATM_ENB signal will not be asserted again until
RATM_CLAV is asserted and the device is ready to accept an entire cell. The
maximum supported clock rate is 52 MHz.
Figure 101 SNK_INTF Start-of-Transfer Timing (Utopia 1 ATM Mode)
D1
D2
D3
D4
D5
D6
P1
P2
P3
P4
P5
P6
RATM_CLK(i)
RATM_CLAV(i)
RATM_SOC(i)
RATM_DATA(i)
RATM_PRTY(i)
RATM_ENB(o)
Note that in ATM master mode the SNK_INTF uses cell based handshaking, thus
once a transfer has begun, RATM_ENB will be asserted continuously until the
end of the cell regardless of the state of RATM_CLAV. Figure 102 shows the
end of transfer signal behavior. In this example, since the PHY slave does not
have another cell to deliver, the RATM_CLAV signal is deasserted after the last
byte is delivered. Also, the AAL1GATOR acting as an ATM master always
deasserts the RATM_ENB at the end of a cell transfer. RATM_CLAV is then
sampled again on the following clock cycle, and if asserted, RATM_ENB will be
asserted again for a new transfer.