Receive Operation - NEC UPD98413 User Manual

(2) Status polling (Packet-level mode)
In the status polling mode, the POS device can receive the µPD98413 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.
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.
TFCLK
TADR[1:0]
PORT0 PORT1
PTPA
DTPA0
DTPA1
DTPA2
DTPA3

4.3.4 Receive operation

In the receive interface, the µPD98413 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 µPD98413 informs the POS device of the selected port by
asserting RSX with the port address on the RDAT bus.
RFCLK
RENB_B
RSX
RSOP
REOP
RERR
RMOD[1:0]
RDAT[31:0]
RPRTY
RVAL
134
CHAPTER 4 INTERFACES
Figure 4-16. Status Polling Timing
PORT2 PORT3 PORT0
PORT0 PORT1 PORT2 PORT3
Figure 4-17. Receive Timing
A(0) D1 D2 D3 D4 D5 D6
PRELIMINARY
The FIFO availability information indicated by PTPA is
PORT1 PORT2 PORT0 PORT1
PORT3 PORT0 PORT1 PORT2 PORT0
D7 D8 D9 D10
PORT2 PORT3
PORT1 PORT2 PORT3
A(2) D1 D2
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