SMC Networks SMC91C95 - Manual (Page 48)

48
I/O SPACE - BANK1
OFFSET NAME TYPE SYMBOL
0 CONFIGURATION REGISTER READ/WRITE CR
The Configuration Register holds bits that define the device configuration and are not expected to change
during run-time. This register is part of the EEPROM saved setup in ISA mode only. In PCMCIA mode, this
register is initialized to the state as defined below the corresponding bits as if no EEPROM was present in
ISA mode (i.e. ENEEP pin is a don’t care in PCMCIA mode).
HIGH
BYTE
0 NO
WAIT
FULL
STEP
SET
SQLCH
AUI
SELEC
T
0 X X 0 X 0 0 0
LOW
BYTE
16 BIT DIS
LINK
Reserved INT
SEL1
INT
SEL0
Function
of EN16
pin
0 1 1 0 0 0 X
NO WAIT - When set, does not request additional
wait states. An exception to this are accesses to
the Data Register if not ready for a transfer. When
clear, negates IOCHRDY for two to three 20 MHz
clocks on any cycle to the SMC91C95.
FULL STEP - This bit is used to select the
signaling mode for the AUI port. When set the AUI
port uses full step signaling. Defaults low to half
step signaling. This bit is only meaningful when
AUI SELECT is high.
SET SQLCH - When set, the squelch level used
for the 10BASE-T receive signal is 240mV. When
clear the receive squelch level is 400mV. Defaults
low.
AUI SELECT - When set the AUI interface is used,
when clear the 10BASE-T interface is used.
Defaults low.
16BIT - Used in conjunction with nEN16 and IOis8
(in PCMCIA mode only) to define the width of the
system bus. If the nEN16 pin is low, this bit is
forced high. Otherwise the bit defaults low and can
be programmed by the host CPU.
DIS LINK - This bit is used to disable the 10BASE-
T link test functions. When this bit is high the
SMC91C95 disables link test functions by not
generating nor monitoring the network for link
pulses. In this mode the SMC91C95 will transmit
packets regardless of the link test, the EPHSR
LINK_OK bit will be set and the LINK LED will stay
on. When low the link test functions are enabled. If
the link status indicates FAIL, the EPHSR
LINK_OK bit will be low, while transmit packets
enqueued will be processed by the SMC91C95,
transmit data will not be sent out to the cable.
INT SEL1-0 - In ISA mode, used to select one out
of four interrupt pins. The three unused interrupts
are tristated.