CHAPTER 4 INTERFACES
PRELIMINARY
NEC confidential and Proprietary
134
(2) Status polling (Packet-level mode)
In the status polling mode, the POS device can receive the
µ
PD98413 port FIFO status information through the
polling mechanism. In this mode, PTPA is used. DTPA1-3 are not used, and these signals are fixed to low.
Figure4-18 is an example of the status polling timing. The status of a given port is determined by setting the
polling address TADR[1:0] to the port address. The polled transmit packet available signal PTPA is updated with
the transmit FIFO status in a pipelined manner. The FIFO availability information indicated by PTPA is
programmable by the FTHT register.
The POS device is not restricted in its polling order. The PTPA signal allows polling other ports at any time,
including while a data transfer is in progress.
In the status polling mode, a data transfer is same operation as the direct status indication mode.
Figure 4-16. Status Polling Timing
TFCLK
TADR[1:0]
PORT0 PORT1 PORT2
PORT0
PORT1
PTPA
PORT0
PORT3
PORT1 PORT2
PORT2 PORT0 PORT1 PORT2
PORT3
PORT3 PORT3 PORT0
PORT1
PORT2 PORT0 PORT1 PORT2
PORT3
DTPA0
DTPA1
DTPA2
DTPA3
4.3.4 Receive
operation
In the receive interface, the
µ
PD98413 selects the port by itself, which there is a receive data in the receive FIFO
and it should send the data to the POS device. This selection will be serviced in a round-robin fashion. Traditional
polling schemes for the receive side are not supported.
(1) Normal receive operation
The receive interface is controlled by the POS device using the RENB_B signal. All signals are updated using the
rising edge of RFCLK, when RENB_B is asserted.
Figure is an example of the receive timing. The
µ
PD98413 informs the POS device of the selected port by
asserting RSX with the port address on the RDAT bus.
Figure 4-17. Receive Timing
RFCLK
RSOP
RMOD[1:0]
REOP
RERR
RENB_B
RSX
RDAT[31:0]
RPRTY
RVAL
A(0)
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
A(2)
D1
D2
Содержание NEASCOT-P65
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