CY7C68053
Document # 001-06120 Rev *F Page 36 of 39
9.13.4 Sequence Diagram of a Single and Burst Asynchronous Write
Figure 9-18 illustrates the timing relationship of the SLAVE
FIFO write in an asynchronous mode. The diagram shows a
single write followed by a burst write of 3 bytes and committing
the 4-byte-short packet using PKTEND.
• At t = 0 the FIFO address is applied, ensuring that it meets
the set-up time of tSFA. If SLCS is used, it must also be
asserted (SLCS may be tied low in some applications).
• At t = 1 SLWR is asserted. SLWR must meet the minimum
active pulse of tWRpwl and minimum de-active pulse width
of tWRpwh. If the SLCS is used, it must be asserted with
SLWR or before SLWR is asserted.
• At t = 2, data must be present on the b us tSFD before the
deasserting edge of SLWR.
• At t = 3, deasserting SLWR causes the data to be written
from the data bus to the FIFO and then the FIFO pointer is
incremented. The FIFO flag is also updated after tXFLG from
the deasserting edge of SLWR.
The same sequence of events is shown for a burst write and
is indicated by the timing marks of T = 0 through 5. Note In the
burst write mode, once SLWR is deasserted, the data is written
to the FIFO and then the FIFO pointer is incremented to the
next byte in the FIFO. The FIFO pointer is post incremented.
In Figure9-18 once the fo ur bytes are written to the FIFO and
SLWR is deasserted, the short 4-byte packet can be
committed to the host using the PKTEND. The external device
must be designed to not assert SLWR and the PKTEND signal
at the same time. It must be designed to assert the PKTEND
after SLWR is deasserted and meet the minimum deasserted
pulse width. The FIFOADDR lines are to be held constant
during the PKTEND assertion.
PKTEND
SLWR
FLAGS
DATA
Figure 9-18. Slave FIFO Asynchronous Write Sequence and Timing Diagram[17]
tWRpwh
tWRpwl
tXFLG
N
tSFD
N+1
tXFLG
tSFA tFAH
FIFOADR
SLCS
tWRpwh
tWRpwl tWRpwh
tWRpwl tWRpwh
tWRpwl
tFAH tSFA
tFDH tSFD
N+2
tFDH tSFD
N+3
tFDH
tSFD tFDH
tPEpwh
tPEpwl
t=0
t=2
t =1 t=3
T=0
T=2
T=1 T=3 T=6 T=9
T=5 T=8
T=4 T=7
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