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78 www.xilinx.com SPI-4.2 Lite v4.3 User Guide
UG181 June 27, 2008
Chapter 4: Designing with the Core
R
containing the end-of-packet information for channel 2. Finally, the start-of-packet and
address information for channel 3 are sent in the payload control word (C3).
If the payload control words did not contain SOP indications (such as payload resumes),
the Source core would not be required to enforce minimum SOP spacing. The Source core
will then pack the EOP and Payload Control word into a single cycle and will not insert
idle cycles. This behavior is illustrated in Figure 4-23.
The Source core formats the data to be written onto the SPI-4.2 Lite bus (TDat). Table 4-6
shows an example of the formatting that this block does with the data read-out of the
Source FIFO (control words are binary and payload transfers are hexadecimal). When an
SOP is read out of the FIFO, the following 16-bit word transfer sent on the SPI-4.2 data bus
is an SOP control word. This example shows the receipt of an SOP for channel 2 and two
Figure 4-22: Source Data Path - Minimum SOP Spacing Enforced
Figure 4-23: Source Data Path - Short Packet Transfers
CH1
1A 1B -- --
CH2
3A 3B -- --2A 2B 2C --
100 100110
SrcFFClk
SrcFFWrEn_n
SrcFFAddr
SrcFFData
SrcFFMod
SrcFFSOP
SrcFFEOP
TDat_P
TDClk_P
TCtl_P
1A 1B I I I C2 2A 2B I I I I
C3
IC1
CH3
I1A 1B I I I
C2
2A 2B 2CI
C1
I
CH1
1A 1B -- --
CH2
3A 3B -- --2A 2B 2C --
100 100110
SrcFFClk
SrcFFWrEn_n
SrcFFAddr
SrcFFData
SrcFFMod
SrcFFSOP
SrcFFEOP
TDat_P
TDClk_P
TCtl_P
1A C2 2A 2B
C3
C1
CH3
I1A 1B
C2
2A 2B 2C
C1