Digilent D2-SB Справочное руководство - Страница 4
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D2-SB Reference Manual
System Bus
The "system bus" is a protocol used by certain
expansion boards that mimics a simple 8-bit
microprocessor bus. It uses eight data lines,
six address lines, a write-enable (WE) strobe
that can be used by the peripheral to latch
written data, an output-enable (OE) strobe that
can be used by the peripheral to enable read
data, a chip select, and a clock to enable
synchronous transfers.
Write Cycle
WE
DB0-DB7
Read Cycle
OE
WE
DB0-DB7
Symbol
www.digilentinc.com
CS
OE
ten
Time to enable after CS asserted
th
Hold time
tdoe
Time to disable after OE de-asserted
teoe
Time to enable after OE asserted
tw
Write strobe time
tsu
Data setup time
twd
Write disable time
The diagrams below show signal timings
assumed by Digilent to create peripheral
devices. However, any bus and timing models
can be used by modifying circuits in the FPGA
and attached peripheral devices.
ten
tdoe
tw
tsu
teoe
twd
tsu
Parameter
th
teoe
th
tdoe
th
th
Read data latch time
Time (typ)
10ns
1ns
10ns
15ns
10ns
5ns
0ns
Digilent, Inc.
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