H O S T I N T E R F A C E
Data Device Corporation
DS-BU-67301B-G
1/14
87
Figure 47. Timing for Assertion of CPU_nSTOP - Output During Synchronous Burst
Write Transfer
Figure 47 Note:
In this example, the fourth word written by the host results in the filling of the Total-
AceXtreme®’s command FIFO to its capacity. The capacity of the command FIFO is
software programmable for either 32, 16, or 8 words. As a result, the Total-
AceXtreme will not be able to accept any further additional word transfers until one or
more commands are drained from the FIFO. At this time, the Total-AceXtreme will
terminate the current transfer by asserting its CPU_nSTOP output low.
If this occurs, it is recommended for the host to delay before attempting to retry the
current multi-word transfer. To ensure that the FIFO has drained sufficiently, the host
should delay for sufficient time to allow at least half of the words in the FIFO to be
drained. Assuming that the FIFO is fully populated with register write transfer
commands, these require 25 ns each to drain. Therefore, the minimum delay times to
prevent a subsequent “STOP” condition are 425 ns for a 32-word command FIFO;
225 ns for a 16-word command FIFO; and 125 ns for an 8-word command FIFO.
CPU_DATA
HOST_CLK
nDATA_RDY
CPU_WORD_EN[1:0]
RD_nWR
MEM_nREG
CPU_ADDR
nDATA_STRB
nSELECT
CPU_nLAST
CPU_nSTOP
tCLK
tDH
tRDD
tAS
tCS
tSH
tCH
Data
Data
Data
tLH
tDS
Address
tWait
Data
tDH
tAS
tAS
tAS
tAH
tAH
tAH
tAH
tLS
tSS
tSHC
tSTPD
Last Valid Data
Data
Data
tSTPD
tRDD