Table 12-14.
DMA to AT-Bus, On-board I/O, and ROM----Input Requirements
16MHz
20MHz
Symbol
Parameters
Min.
Max.
Min.
Max.
t210
HLDA setup before BUSCLK rise
DREQ setup before BUSCLK rise
DREQ hold after BUSCLK rise
IOCHRDY setup before BUSCLK rise
IOCHRDY hold after BUSCLK rise
20
----
15
----
t212
20
----
15
----
t213
20
----
15
----
t214
15
----
10
----
t215
7
----
5
----
Certain input parameters, as noted, are nonrestrictive. The signal may not be recognized until the
period if these parameters are violated. The parameter specifies only the condition needed to guara
signal on a particular clock edge.
subsequent clocking
ntee recognition of the
DMA and AT-Bus Master Access to Local Memory
Tables 12-15 through 12-17 are the specification requirements for the DMA and the AT
bus master to access local memory. Note: For XD, D, and PAR timing, use t145-t148
and t112. For row/column change over and CAS active, use t102, t105, and t107.
Table 12-15.
DMA and AT-Bus Master Access to Local Memory----Output Responses
16MHz
20MHz
Symbol
Parameters
Min.
Max.
Min.
Max.
t230
-RAS high from HLDA rise
----
60
----
60
t231
A0-23 and -BHE float from -MASTER active
----
60
----
60
t232
Command float from -MASTER active
----
35
----
30
t233
-MWE rise from -XMEMR fall
----
45
----
40
t234
-MWE fall from -CAS rise
2
60
2
60
t235
-RAS inactive from -XMEMR or -XMEMW high
----
45
----
42
t236
-CAS inactive from -XMEMR or -XMEMW high
----
55
----
50
t239
-RAS active from XMEMR or XMEMW
----
36
----
36
t240
A20 valid from MODA20 during MASTER access
----
25
----
25
t241
A0 valid from MODA0 during MASTER access
----
24
----
24
t242
SDIRL, H fall from -XMEMW fall during Master
write
----
40
----
40
System Characteristics
AC Characteristics 16- and 20MHz
I
Chips and Technologies, Inc.
P R E L I M I N A R Y
Revision 3.0
12-9