CY7C68053
Document # 001-06120 Rev *I
Page 35 of 40
9.13.3 Sequence Diagram of a Single and Burst Asynchronous Read
Figure 23 illustrates the timing relationship of the SLAVE FIFO
signals during an asynchronous FIFO read. It shows a single
read followed by a burst read.
■ At t = 0, the FIFO address is stable and the SLCS signal is
asserted.
■ At t = 1, SLOE is asserted. This results in the data bus being
driven. The data that is driven on to the bus is previous data;
it is data that was in the FIFO from a prior read cycle.
■ At t = 2, SLRD is asserted. The SLRD must meet the minimum
active pulse of tRDpwl and minimum inactive pulse width of
tRDpwh. If SLCS is used then, SLCS must be asserted before
SLRD is asserted (that is, the SLCS and SLRD signals must
both be asserted to start a valid read condition).
■ The data that is driven, after asserting SLRD, is the updated
data from the FIFO. This data is valid after a propagation delay
of tXFD from the activating edge of SLRD. In Figure 23, data N
is the first valid data read from the FIFO. For data to appear on
the data bus during the read cycle (for example, SLRD is
asserted), SLOE MUST be in an asserted state. SLRD and
SLOE can also be tied together.
The same sequence of events is also shown for a burst read
marked with T = 0 through 5.
Note In burst read mode, during SLOE assertion, the data bus
is in a driven state and outputs the previous data. Once SLRD is
asserted, the data from the FIFO is driven on the data bus (SLOE
must also be asserted) and then the FIFO pointer is
incremented.
SLRD
FLAGS
SLOE
DATA
Figure 23. Slave FIFO Asynchronous Read Sequence and Timing Diagram[16]
tRDpwh
tRDpwl
tOEon
tXFD
tXFLG
N
Data (X)
tXFD
N+1
tXFD
tOEoff
N+3
N+2
tOEoff
tXFLG
tSFA
tFAH
FIFOADR
SLCS
Driven
tXFD
tOEon
tRDpwh
tRDpwl
tRDpwh
tRDpwl
tRDpwh
tRDpwl
tFAH
tSFA
N
t=0
T=0
T=1
T=7
T=2
T=3
T=4
T=5
T=6
t=1
t=2
t=3
t=4
NN
SLOE
SLRD
FIFO POINTER
N+3
FIFO DATA BUS Not Driven
Driven: X
N
Not Driven
SLOE
N
N+2
N+3
Figure 24. Slave FIFO Asynchronous Read Sequence of Events Diagram
SLRD
N
N+1
SLRD
N+1
SLRD
N+1
N+2
SLRD
N+2
SLRD
N+2
N+1
SLOE
Not Driven
SLOE
N
N+1
N+1
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