AM79C961AVIW AMD (ADVANCED MICRO DEVICES), AM79C961AVIW Datasheet - Page 50

• Manufacturer Part Number: AM79C961AVIW
• Manufacturer: AMD (ADVANCED MICRO DEVICES)

Specifications of AM79C961AVIW

• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (min): 4.75V
• Operating Supply Voltage (max): 5.25V
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 144
• Lead Free Status / Rohs Status: Not Compliant

are enabled. This pattern must be sequential, i.e., any
other I/O access to this I/O port will reset the state
machine which is checking the pattern. Interrupts
should be disabled during this time to eliminate any
extraneous I/O cycles.
The exact sequence for the initiation key is listed below
in hexadecimal.
6A, B5, DA, ED, F6, FB, 7D, BE
DF, 6F, 37, 1B, 0D, 86, C3, 61
B0, 58, 2C, 16, 8B, 45, A2, D1
E8, 74, 3A, 9D, CE, E7, 73, 39
Isolation Protocol
A simple algorithm is used to isolate each Plug and
Play card. This algorithm uses the signals on the ISA
bus and requires lock-step operation between the Plug
and Play hardware and the isolation software.
50
No
Read from serial
isolation register
Read all 72 bits
Wait for next read from serial isolation register
Drive “AAH”
on SD[7:0]
Drive “55H”
on SD[7:0]
from serial
identifier
Isolated
Card
Yes
One
Yes
After I/O read
completes, fetch
next ID bit from
serial identifier
Plug and Play ISA Card
Isolation Algorithm
ID bit = “1H”
Isolation
Leave SD in
high-impedance
State
Leave SD in
high-impedance
Get one bit from
serial identifier
No
No
No
SD[1:0] = “10"
SD[1:0] = “01"
Yes
Yes
Sleep
State
ID = 0;
other card
ID = 1
19364B-12
Am79C961A
The key element of this mechanism is that each card
contains a unique number, referred to as the serial
identifier for the rest of the discussion. The serial iden-
tifier is a 72-bit unique, non-zero, number composed of
two, 32-bit fields and an 8-bit checksum. The first 32-bit
field is a vendor identifier. The other 32 bits can be any
value, for example, a serial number, part of a LAN
address, or a static number, as long as there will never
be two cards in a single system with the same 64 bit
number. The serial identifier is accessed bit-serially by
the isolation logic and is used to differentiate the cards.
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 initiation key, described
earlier, puts all cards into configuration mode. The
hardware on each card expects 72 pairs of I/O read
accesses to the READ_DATA por t. The card’s
response to these reads depends on the value of each
bit of the serial identifier which is being examined one
bit at a time in the sequence shown above.
If the current bit of the serial identifier is a “1", then the
card will drive the data bus to 0x55 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 imped-
ance will check the data bus during the I/O read cycle
to sense if another card is driving D[1:0] to “01". During
the second I/O read, the card(s) that drove the 0x55,
will now drive a 0xAA. All high impedance cards will
check the data bus to sense if another card is driving
D[1:0] to “10". Between pairs of Reads, the software
should wait at least 30 s.
If a high impedance card sensed another card driving
the data bus with the appropriate data during both
cycles, then that card ceases to participate in the cur-
rent iteration of card isolation. Such cards, which lose
out, will participate in future iterations of the isolation
protocol.
Note: During each read cycle, the Plug and Play hard-
ware drives the entire 8-bit databus, but only checks
the lower 2 bits.
Check-
sum
Byte
0
Byte
3
Byte
2
Shifting of Serial Identifier
Number
Serial
Byte
1
Byte
0
Byte
3
Byte
2
Vendor
Byte
ID
1
Byte
0
19364B-13
Shift