AM79C972BVD\W AMD (ADVANCED MICRO DEVICES), AM79C972BVD\W Datasheet - Page 77
AM79C972BVD\W
Manufacturer Part Number
AM79C972BVD\W
Description
Manufacturer
AMD (ADVANCED MICRO DEVICES)
Datasheet
1.AM79C972BVDW.pdf
(130 pages)
Specifications of AM79C972BVD\W
Operating Supply Voltage (typ)
3.3V
Operating Temperature Classification
Commercial
Mounting
Surface Mount
Lead Free Status / RoHS Status
Compliant
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The EROMCS is driven low for the value ROMTMG +
1. Figure 43 assumes that ROMTMG is set to nine.
EBD[7:0] is sampled with the next rising edge of CLK
ten clock cycles after EBUA_EBA[7:0] was driven with
a new address value. This PCI slave access to the
Flash/EPROM will result in a retry for the very first ac-
cess. Subsequent accesses may give a retry or not, de-
pending on whether or not the data is present and valid.
The access time is dependent on the ROMTMG bits
(BCR18, bits 15-12) and the Flash/EPROM. This ac-
cess mechanism differs from the Expansion ROM ac-
cess mechanism since only one byte is read in this
manner, instead of the 4 bytes in an Expansion ROM
access. The PCI bus will not be held during accesses
through the Expansion Bus Data Port. If the LAAINC
EBUA_EBA [7:0]
Latched Address
EBDA [15:8]
EROMCS
AS_EBO
DEVSEL
FRAME
TRDY
IRDY
EBD
CLK
EBUA_EBA[7:0]
EBDA[15:8]
AS_EBOE
EROMCS
EBD[7:0]
5
Figure 43. Flash Read from Expansion Bus Data Port
CLK
Figure 42. Expansion ROM Bus Read Sequence
10
A[19:16]
15
EBUA[19:16]
1
20
A[7:2], 0, 0
2
Am79C972
25
3
4
30
(BCR29, bit 15) is set, the EBADDRL address will be
incremented and a continuous series of reads from the
Expansion Data Port (EBDATA, BCR30) is possible.
The address incrementor will roll over without warning
and without incrementing the upper address EBAD-
DRU.
The Flash write is almost the same procedure as the
read access, except that the Am79C972 controller will
not drive AS_EBOE low. The EROMCS and EBWE are
driven low for the value ROMTMG again. The write to
the FLASH port is a posted write and will not result in a
retry to the PCI unless the host tries to write a new
value before the previous write is complete, then the
host will experience a retry. See Figure 44.
5
A[7:2], 0, 1
6
35
7
EBDA[15:8]
EBA[7:0]
8
40
A[7:2], 1, 0
9
45
10
11
50
12 13
55
A[7:2], 1, 1
60
21485C-45
21485C-46
66
77
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