User guide
CY7C68013A, CY7C68014A
CY7C68015A, CY7C68016A
Document Number: 38-08032 Rev. *X Page 56 of 71
9.17.4 Sequence Diagram of a Single and Burst Asynchronous Write
Figure 9-23. Slave FIFO Asynchronous Write Sequence and Timing Diagram
[24]
Figure 9-23 shows 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
4byte short packet using PKTEND.
■ At t = 0 the FIFO address is applied, ensuring that it meets the
setup time of t
SFA
. 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 t
WRpwl
and minimum de-active pulse width of
t
WRpwh
. 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 bus t
SFD
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 increments the FIFO pointer.
The FIFO flag is also updated after t
XFLG
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, after 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 Figure 9-23, after the four bytes are written to the FIFO and
SLWR is deasserted, the short 4-byte packet can be committed
to the host using PKTEND. The external device should be
designed to not assert SLWR and the PKTEND signal at the
same time. It should be designed to assert the PKTEND after
SLWR is deasserted and met the minimum deasserted pulse
width. The FIFOADDR lines have to held constant during the
PKTEND assertion.
PKTEND
SLWR
FLAGS
DATA
t
WRpwh
t
WRpwl
t
XFLG
N
t
SFD
N+1
t
XFLG
t
SFA
t
FAH
FIFOADR
SLCS
t
WRpwh
t
WRpwl
t
WRpwh
t
WRpwl
t
WRpwh
t
WRpwl
t
FAH
t
SFA
t
FDH
t
SFD
N+2
t
FDH
t
SFD
N+3
t
FDH
t
SFD
t
FDH
t
PEpwh
t
PEpwl
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