參數(shù)資料
型號： DM9008F
廠商： Electronic Theatre Controls, Inc.
英文描述： ISA/Plug & Play Super Ethernet Contoller
中文描述： 的ISA /插頭
文件頁數(shù)： 32/68頁
文件大?。?/td> 403K
代理商： DM9008F
DM9008
ISA/Plug & Play Super Ethernet Contoller
32
Final
Version :DM9008-DS-F02
June 14, 2000
Serial Identifier
The key element of the Plug and Play isolation protocol is that
each card contains a unique number called a serial identifier.
The serial identifier is a 72-bit unique, non-zero number
composed of two 32-bit fields and 8-bit checksum. The first
32-bit field is a vendor identifier. The other 32 bits can be any
value, such as a serial number, part of a LAN address or a
static number, as long as no two cards in a single system have
the same 64-bit number. The serial identifier is accessed bit-
serially by isolation logic, and is used to differentiate the cards.
Figure 2. Shifting of Serial Identifier
The shift order for all Plug and Play serial isolation and
resource data is defined as bit[0], bit[1], and so on through
bit[7].
Hardware Protocol
The isolation protocol can be invoked by the Plug and Play
software at any time. The previously described Initiation Key
puts all cards into configuration mode. The hardware for each
card expects 72 pairs of I/O read accesses to the
READ_DATA port. The card's response to these reads
depends on the value for each bit of the serial identifier, which
is examined one bit at a time, as shown in Figure 1.
If the current bit of the serial identifier is a "1", then the card will
drive the data bus to 55H to complete the first I/O read cycle. If
the bit is "0", then the card puts its data bus driver into high
impedance. All cards in high impedance will check the data
bus during the I/O read cycle to sense if another card is driving
SD[1:0] to "01". During the second I/O read, the card(s) that
drove the 55H will now drive a AAH. All high impedance cards
will check the data bus to sense if another card is driving
SD[1:0] to "10".
If a high impedance card senses another card driving the data
bus with the appropriate data during both cycles, it ceases to
participate in the current iteration of card isolation. Such cards,
which lose out, will participate in future iterat-ions of the
isolation protocol.
NOTE: During each read cycle, the Plug and Play
hardware drives the entire 8-bit data bus, but
checks only the lower 2 bits.
If a card is driving the bus or is in high impedance state and
does 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, using 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 participate in subsequent
iterations of the isolation protocol. Cards must be assigned a
CSN before they will respond to the other PnP commands.
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