83C795 Datasheet, PDF (71/136 Pages) List of Unclassifed Manufacturers – Ethernet System Controller

83C795
HOST INTERFACE SECTION
Port Name
Location
Type
ADDRESS
Fixe d a t 0279h Write-only
(LPT2 Status Port)
WRITE_DATA Fixed at 0A79h Write-only
(LPT2 Status Port
+ 0800h)
READ_DATA Re lo ca tab le in Read-only
range 0200h –
03FFh
TABLE 6-6. AUTO-CONFIGURATION PORTS
All writes to the ADDR E S S port are s tored in an
address register. T he value in this regis ter is us ed
as an index into the internal 256-byte range that
holds the P nP configur ation regis ters . Any
acces s es totheWR IT E _DAT Aor R E AD_DAT Aport
will be to the PnP configuration regis ter that is
currently indexed by the addres s register. S ee
s ection 6.8.3 for details on the configuration
regis ters.
6.8.2 Plug And Play States
T he main Plug and Play s tate machine contains
four states and is illustrated in F igure 6-7.
All cards will enter the WaitF orK ey s tate in
res pons e to either a power-up res et or the R es et
and Wait for Key commands . No commands are
activein this s tateuntil the Initiation Key is detected
on the IS Abus . T he WaitF orKey s tate is the default
s tate for PlugandPlay cards duringnormal sys tem
operation. T he Initiation Key places the Plug and
Play s tate machine into the S leep s tate. T he
Initiation Key cons is ts of a predefined series of
writes to the ADDR E S S port. T he write s equence
is decodedby on-cardlogic. If theproper s equence
of I/O writes is detected, the Plug and Play
auto-configur ation ports are enabled. T he
s equence of writes that are expected is :
0x6A,0xB5,0xDA,0xED,0xF6,0xFB,0x7D,0xBE,
0xDF,0x6F,0x37,0x1B,0x0D,0x86,0xC3,0x61,
0xB0,0x58,0x2C,0x16,0x8B,0x45,0xA2,0xD1,
0xE8,0x74,0x3A,0x9D,0xCE,0xE7,0x73,0x39
FIGURE 6-7. PLUG AND PLAY STATE MACHINE
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