Altera POS-PHY Level 2 and 3 Compiler - Manual (Page 48)

3–20 Chapter 3: Functional Description
Interface Signals
POS-PHY Level 2 and 3 Compiler User Guide © November 2009 Altera Corporation
Preliminary
1 These signals are compliant with the POS-PHY Level 3 Specification, Issue 4, June
2000.
Table 3–10. POS-PHY Level 3 Receive Interface (Part 1 of 2)
Signal Direction Description
rfclk Input Receive FIFO buffer write clock. rfclk is used to synchronize data-transfer
transactions between the link-layer device and the PHY-layer device. rfclk can
cycle at a rate up to 104 MHz.
rdat[31/7:0] PHY to link Receive packet data bus. The rdat bus carries the packet octets that are read from
the receive FIFO buffer. rdat is valid only when rval is asserted. Data must be
received in big-endian order on rdat. When an 8-bit interface is used, only
rdat[7:0]
is supported.
rsop PHY to link Receive start of packet. rsop delineates the packet boundaries on the rdat bus.
When rsop is high, the start of the packet is present on the rdat bus. rsop must
be present at the beginning of every packet and is valid only when rval is
asserted.
reop PHY to link Receive end of packet. reop delineates the packet boundaries on the rdat bus.
When reop is high, the end of the packet is present on the rdat bus. rmod
indicates the number of valid bytes the last double-word is composed of, when
reop
is asserted. reop is required to be present at the end of every packet and is
valid only when rval is asserted.
rerr PHY to link Receive error indicator. rerr is used to indicate that the current packet is aborted
and should be discarded. rerr should only be asserted when reop is asserted.
Conditions that can cause rerr to be set can be, but are not limited to, FIFO buffer
overflow, abort-sequence detection, missing SOP, missing EOP, and parity errors.
terr
is asserted at its input. rerr is valid only when rval is asserted.
rmod[1:0] PHY to link Receive word modulo signal. rmod indicates the number of valid bytes of data in
rdat
. The rmod bus should always be all zero, except during the last double-word
transfer of a packet on rdat. When reop is asserted, the number of valid packet
data bytes on rdat is specified by rmod
When rmod[1:0] = ‘00’ rdat[31:0] is valid.
When rmod[1:0] = ‘01’ rdat[31:8] is valid.
When rmod[1:0] = ‘10’ rdat[31:16] is valid.
When rmod[1:0] = ‘11’ rdat[31:24] is valid
rmod is valid only when rval is asserted.
rprty PHY to link Receive parity signal. rprty indicates the parity calculated over the rdat bus.
When rprty is supported, the PHY-layer device must support both odd and even
parity.
renb Link to PHY Receive read enable (see Figure 3–16 ). renb controls the flow of data from the
receive FIFO buffers. During data transfer, rval must be monitored, as it indicates
if rdat, rprty, rmod, rsop, reop, rsx, and rerr are valid. The system can
deassert renb at anytime, if it is unable to accept data from the PHY device. When
renb
is sampled low by the PHY device, a read is performed from the receive FIFO
buffer. rdat, rprty, rmod, rsop, reop, rerr, rsx, and rval are updated
on the following rising edge of rfclk. When renb is sampled low by the PHY
device, a read is not performed and rdat, rprty, rmod, rsop, reop, rerr,
rsx
, and rval are not updated on the following rising edge of rfclk.