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(2) Receive interface
The receive interface uses the signals defined below.
RFCLK
Receive FIFO write clock.
RFCLK is used to synchronize data transfer transactions between the µPD98413 and the POS
(input):
device. RFCLK cycles at a rate up to 104MHz.
RDAT[31:0]
Receive packet data bus.
(output):
RDAT[31:0] carries the receive packet data and the in-band port address. The RDAT bus is
considered valid only when RVAL is asserted. RDAT31 is the MSB, RDAT0 is the LSB.
RSOP
Receive start of packet.
(output):
RSOP is used to delineate the packet boundaries on the RDAT bus. When RSOP is high, the
start of the packet is present on the RDAT bus. RSOP is considered valid only when RVAL is
asserted.
RENB_B
Receive read enable.
(input):
RENB_B is used to control the flow of data from the receive FIFO. When RENB_B is low, the
RDAT, RPRTY, RMOD, RSOP, REOP, RERR, RSX and RVAL signals are updated on the
following rising edge of RFCLK.
When RENB_B is high, the RDAT, RPRTY, RMOD, RSOP, REOP, RERR, RSX and RVAL
signals will remain unchanged on the following rising edge of RFCLK.
RPRTY
Receive bus parity.
(output):
RPRTY indicates the parity calculated over the RDAT bus. RPRTY is considered valid only
when RVAL or RSX is asserted.
The µPD98413 supports the odd or even parity.
REOP
Receive end of packet.
(output):
REOP is used to delineate the packet boundaries on the RDAT bus. When REOP is high, the
data on RDAT is assumed to be the end of a packet, and the valid bytes of the last word are
indicated by RMOD[1:0]. REOP is considered valid only when RVAL is asserted.
RMOD[1:0]
Receive word modulo.
(output):
RMOD[1:0] indicates the valid bytes of the transmit data on RDAT[31:0]. When REOP is
asserted, the valid bytes on RDAT[31:0] are specified by RMOD[1:0] below.
00: RDAT[31:0] is valid.
01: RDAT[31:8] is valid.
10: RDAT[31:16] is valid.
11: RDAT[31:24] is valid.
RMOD[1:0] is considered valid only when RVAL is asserted. RMOD[1:0] is 0, except during the
last word transfer of a packet.
CHAPTER 4 INTERFACES
PRELIMINARY
NEC confidential and Proprietary
131
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