83C795 Datasheet, PDF (29/136 Pages) List of Unclassifed Manufacturers – Ethernet System Controller

83C795
ETHERNET SYSTEM CONTROLLER REGISTERS
5.1.5 HWR - Hardware Support Register
R ead/Write Port = 04
T his regis ter is us ed to control general purpose
outputs and to s witch between configuration and
LAN Addres s regis ters .
BIT
HWR READ
7 SWH
6—
5 ETHR
4 HOST16
3—
2 ISTAT
1 PNPJMP
0 GPOE
RESET
0
0
1
0
0
0
JMP6
0
BIT
HWR WRITE
7 SWH
6—
5—
4—
3 NUKE
2—
1—
0 GPOE
RESET
0
0
1
0
0
0
0
0
Bit 7: SWH, Switch Register Set
T his bit s elects between the LAN Addres s regis ters
andtheBoardConfiguration regis ters in theregis ter
map where:
SWH = 0 - LAN Address Registers are visible
SWH = 1 - Configuration Registers are visible
Bit 5: ETHER, MAC Protocol Type
When E T HE R = 1, the 802.3 protocol is provided
by this device. T he 83C795 s upports only 802.3.
Bit 4: HOST16
T his bit reports whether the 83C795 believes it is
connectedto an 8-bit or 16-bit host. T he chipdeter-
mines this by looking at the ME MR pin for activity.
Where:
HOST16 = 0 - 8-bit host
HOST16 = 1 - 16-bit host
Bit 3: NUKE, Restart
T his bit is ’OR ’ed together with the R E S E T pin
s ignal to form the internal R E S E T for the chip.
S etting this bit has the s ame effect on the 83C795
as cyclingpower on the hos t machine. T he chipwill
res et to its initial condition and reload from the
E E R OM. T his bit is cleared when the reset be-
comes effective. T he NUKE res et executes for 256
chip-clock cycles to allow the MA bus to float and
the initialization jumpers to achieve their true val-
ues .
Note
Do not try to access this chip during
reset.
Bit 2: ISTAT, Interrupt Status
IS T AT returns to1 when Network InterfaceControl-
ler has an interrupt active.
Bit 1: PNPJMP, Plug and Play Jumper Installed
A read-only bit that returns a 1 if jumper 6 is in-
s talled. If PNPJMP = 1 and the PNPE N bit (E R -
FAL.0) is s et, then Plug and Play hardware is
enabled.
Bit 0: GPOE, GPX Pin Output Enable
T he output is enabled when GPOE = 1.
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