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RTL8019AS

Realtek Full-Duplex Ethernet Controller with Plug and Play Function (RealPNP)

Realtek Semiconductor 

SPECIFICATION

RTL8019AS

Serial Identifier

The key element of the Plug and Play isolation protocol is that each card contains a unique number,

named serial identifier. The serial identifier 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.

Check-

sum

Byte 0

Byte 3

Serial Number

Byte 2 Byte 1

7:0

7:0

7:0

7:0

Vendor ID

Byte 0 Byte 3 Byte 2 Byte 1

7:0

7:0

7:0

7:0

Byte 0

7:0

Shift

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 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 port. 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 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 card will check the data bus to sense if another

card is driving SD[1:0] to "10."

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 current 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 hardware drives the entire 8-bit data bus, but

only checks the lower 2 bits.

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.

8019AS.doc

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2001-04-02

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