H O S T I N T E R F A C E
Data Device Corporation
DS-BU-67301B-G
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6.4 Synchronous Host Processor Interface
In Synchronous mode, the timing of transfers between the host CPU and the
Total-
AceXtreme®
is controlled by a clock provided by the host and connected to the
Total-AceXtreme’s
HOST_CLK input. The
Total-AceXtreme
can operate with
HOST_CLK speeds up to 80 MHz.
6.4.1 Types of Synchronous Mode Transfers
Within the
Total-AceXtreme’s
Synchronous mode, there are three types of data
transfers that may be performed. These are:
•
Single-word transfers.
•
Sequential burst transfers.
•
Random burst transfers.
Single-word transfers are limited to a single 32-bit transfer or a pair of 16-bit
transfers.
With both sequential and random Synchronous transfers, the host performs a series
of word transfers. In each case, during the active portion of the transfer, a 32-bit or
16-bit word is transferred during each cycle of the
Total-AceXtreme’s
HOST_CLK
input.
With sequential burst transfers, the host CPU presents its starting address once, at
the beginning of the transfer. Following that, a transfer is performed between the host
and the starting address in the
Total-AceXtreme’s
internal shared RAM. After that, a
series of transfers is performed between the host and successive address locations
in the
Total-AceXtreme’s
internal shared RAM.
Random burst Synchronous transfers are not limited to transferring data to or from
successive locations in the
Total-AceXtreme’s
internal memory. During the active
portion of a random Synchronous burst transfer, the host CPU presents a new
memory address during each cycle of HOST_CLK.
6.4.2 Operation of Command FIFO and CPU_nSTOP Signal
The Synchronous burst mode involves the use of a command FIFO within the
Total-
AceXtreme
. The size of the command FIFO is software programmable, with options
of 32, 16, or 8 words. The default size for the FIFO is 32 words.
There is one entry posted in the command FIFO for each 32-bit or 16-bit word to be
written to or read from the
Total-AceXtreme
. This includes the values of the
Total-
