Filter
Top Products
SPI-4.2 Lite v4.3 User Guide www.xilinx.com 55
UG181 June 27, 2008
Sink Core
R
than 14 bytes, four idle cycles are required to meet the SOP spacing requirement. After the
four idle cycles, the transfer begins with a start-of-packet control word (C3) for channel 2.
Next, three clock cycles (of two bytes each) are used to transfer the data associated with
channel 2. The transfer concludes with an end-of-packet control word (C4).
Figure 4-2 also shows the data being read out of the FIFO and indicates with forward
slashes that there is latency in processing and storing the SPI-4.2 data. The first 64-bit word
on the FIFO interface contains the four bytes of valid data received for channel 1. The
control signals SnkFFSOP and SnkFFEOP are active, indicating that this is the start and
end of the packet for channel 1. The second 64-bit word contains the six bytes of valid data
for channel 2, and the control signals SnkFFSOP and SnkFFEOP are both asserted.
Table 4-1 provides example formatting for the data and control received on the SPI-4.2
Interface. This data is formatted and presented on the 64-bit Sink FIFO Interface. Control
words are shown in binary and payload transfers are shown as hexadecimal. After an SOP
is received, the following 16-bit word transfer is left justified when written into the FIFO
(written to the most significant 16 bits). For the 64-bit interface, the 16 bits will be in the
SnkFFData[63:48]. The table shows the receipt of an SOP for channel 2, then a series of
payload word transfers. The DIP-4 parity depends on this control word and any
proceeding transfer, and it is shown in the table as “pppp.”
Following this example, two additional tables show the mapping between SPI-4.2 Control
Words and packet status signals for a 64-bit user interface (Table 4-2) and for a 32-bit user
interface (Table 4-3).
Figure 4-2: Sink Data Path - Short Packet Transfers with Minimum SOP Spacing Enforced
RDat_P
RDClk_P
RCtl_P
1A 1B I I I 2A 2B 2CI I IC1 C3 C4C2
CH1
1A 1B -- --
100
SnkFFClk
SnkFFRdEn_n
SnkFFAddr
SnkFFData
SnkFFMod
SnkFFSOP
SnkFFEOP
CH2
2A 2B 2C --
110