參數(shù)資料
型號(hào): AM79C961A
廠商: Advanced Micro Devices, Inc.
英文描述: PCnet ⑩-ISA II Jumperless, Full Duplex Single-Chip Ethernet Controller for ISA
中文描述: PCnet⑩- 2跳線的ISA,全雙工單芯片以太網(wǎng)控制器為ISA
文件頁數(shù): 42/85頁
文件大小: 1088K
代理商: AM79C961A
42
Am79C961A
P R E L I M I N A R Y
If a card was driving the bus or if the card was in high
impedance and did not sense another card driving the
bus, then it should prepare for the next pair of I/O
reads. The card shifts the serial identifier by one bit and
uses the shifted bit to decide its response. The above
sequence is repeated for the entire 72-bit serial
identifier.
At the end of this process, one card remains. This card
is assigned a handle referred to as the Card Select
Number CSN) that will be used later to select the card.
Cards which have been assigned a CSN will not partic-
ipate in subsequent iterations of the isolation protocol.
Cards must be assigned a CSN before they will
respond to the other commands defined in the
specification.
It should be noted that the protocol permits the 8-bit
checksum to be stored in non-volatile memory on the
card or generated by the on-card logic in real-time. The
same LFSR algorithm described in the initiation key
section of the Plug and Play specification is used in the
checksum generation.
Software Protocol
The Plug and Play software sends the initiation key to
all Plug and Play cards to place them into configuration
mode. The software is then ready to perform the isola-
tion protocol.
The Plug and Play software generates 72 pairs of l/O
read cycles from the READ_DATA port. The software
checks the data returned from each pair of I/O reads for
the 0x55 and 0xAA driven by the hardware. If both
0x55 and 0xAA are read back, then the software
assumes that the hardware had a “1" bit in that posi-
tion. All other results are assumed to be a “0.”
During the first 64 bits, software generates a checksum
using the received data. The checksum is compared
with the checksum read back in the last 8 bits of the
sequence.
There are two other special considerations for the soft-
ware protocol. During an iteration, it is possible that the
0x55 and 0xAA combination is never detected. It is also
possible that the checksum does not match If either of
these cases occur on the first iteration, it must be
assumed that the READ_DATA port is in conflict. If a
conflict is detected, then the READ_DATA port is
relocated. The above process is repeated until a non-
conflicting location for the READ_DATA port is found.
The entire range between 0x203 and 0x3FF is avail-
able, however in practice it is expected that only a few
locations will be tried before software determines that
no Plug and Play cards are present.
During subsequent iterations, the occurrence of either
of these two special cases should be interpreted as the
absence of any further Plug and Play cards (i.e. the last
card was found in the previous iteration). This
terminates the isolation protocol.
Note:
The software must delay 1 ms prior to starting
the first pair of isolation reads, and must
wait 250
μ
sec
between each subsequent pair of isolation reads. This
delay gives the ISA card time to access information
from possibly very slow storage devices.
Plug and Play Card Control Registers
The state transitions and card control commands for
the PCnet-ISA II controller are shown in the following
figure.
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AM79C961A_00 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:PCnet⑩-ISA II Jumperless, Full Duplex Single-Chip Ethernet Controller for ISA
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AM79C961AKCW 制造商:AMD 制造商全稱:Advanced Micro Devices 功能描述:PCnet⑩-ISA II Jumperless, Full Duplex Single-Chip Ethernet Controller for ISA