CHAPTER 4 INTERFACES
PRELIMINARY
NEC confidential and Proprietary
122
Figure 4-8. Back-to-back Cell Transmission (Status Polling)
TXCLK
TXENB_B
TXSOC
TXDATA[31:0]
H1
P1
X
P7
P9
P10
H1
P1
X : Invalid
TXCLAV0
P12
P2
P3
P4
TXPRTY
TXADDR[1:0]
PORT0
PORT1
P11
P12
PORT1
X
PORT2
PORT3
PORT0
P8
X
PORT1
X
4.2.4 Receive
operation
The
µ
PD98413 supports both the direct status indication mode and the status-polling mode (Multi-PHY operation
with 1 RXCLAV).
(1) Direct status indication
The
µ
PD98413 implements a dedicated RXCLAV signal for each of the ports. RXCLAV0 corresponds to the
port0, while RXCLAV3 corresponds to the port3.
The ATM device controls the flow of data from the
µ
PD98413 on a per cell basis. The
µ
PD98413 indicates
receive cell available information to the ATM device. The ATM device can select a port for transfer of a cell when
the port has indicated to the ATM device that it has at least one cell available. The
µ
PD98413 deasserts the
RXCLAV0-3 coincident with RXSOC to indicate that the corresponding port of the
µ
PD98413 has no subsequent
cell available. Once the RXCLAV0-3 has been asserted, it will have to stay asserted until the RXSOC is asserted
on that particular port.
A valid RXADDR[1:0] during the clock cycle before asserting the RXENB_B signal will select the port which will
transfer the next cell across the ATM interface. The
µ
PD98413 decodes this signal and the specified port will be
ready to transfer cell data two clock cycles after RXENB_B goes low. The ATM device must deassert RXENB_B
two cycles before the end of the cell transfer, unless a back-to-back transfer is intended. The decode-response
timing between the RXENB_B and the RXDATA[31:0] is therefore two clock cycles
.
Figure 4-9. Receive Timing (Direct Status Indication)
Summary of Contents for NEASCOT-P65
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