son
Sl#
M/IO#
READY#
MBEN
LOCK#
---
-
1
~
r
1/0
INTERFACING
82289
son
LLOCK#
-
Sl#
CBRO#
--
M/IO# BUSY#
--
READY# BPRO#
-
SYSB
BREo#
-
LOCK#
AEN#
-
BPRN#
82288
son
MRDC#
I-~
Sl#
MWDC#
r-:---
M/IO#
10RC#
I-~
READY#
10WC#
r-;--<>
CENL
INTA#
H--
MB
ALE
CMDLY
DT/R#
AEN#
DEN
CO
80286
MPATIBLE
BUS
TO ADDRESS LATCH
TO DATA
TRANSCEIVER
TO DATA TRANSCEIVER
Figure
8-12.
82288
and
82289
Connections
8.6.6
82258
ADMA Controller
G30107
The 82258 Advanced Direct Memory Access (ADMA) controller performs
DMA
transfers
between main memory and an
I/0
device, typically a magnetic disk or communications
channel, without intervention from the
80386. Shifting the
I/O
processing function from the
80386 to the 82258 improves overall system performance because the 80386 doesn't have to
switch context for every transfer.
The 82258 operates from the CLK output of the 82384 and provides the following advanced
features
that
are not available in previous generations of
DMA
controllers:
• Command chaining to perform multiple commands sequentially
•
Data
chaining to scatter data to separate memory locations and to gather data from
separate locations (this feature
is
useful for demand paging)
8-23
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