35
Table 6 - Powerdown Functions
POWERDOWN
ENTERED POWERDOWN
EXITED POWERS
DOWN:
DOES NOT
POWER DOWN
(B2) Power State
nWAKEUP (Pin) When pin is low
and reset is
inactive
When pin goes
high Ethernet Function
(Link logic
enabled)
Modem Function,
Attribute memory
and PCMCIA
configuration
Registers access,
Link Logic
(B2) Power State
PWRDN bit in
Control Register
When bit is set Write access to
I/O space or
reset
Ethernet Function. Modem function,
Attribute Memory
and PCMCIA
Configuration
Registers access
PCMCIA Attribute Memory: Address 0-
7FFEh
The Attribute Memory is implemented using a
combination of interrnal SRAM and external
parallel EEPROM, ROM or Flash ROM. The
internal SRAM is initialized during power up using
the serial EEPROM. This serial EEPROM in
PCMCIA mode is used for the CIS (Card
Information Structure). If no serial EEPROM is
used, the parallel EEPROM must be used. Internal
CIS RAM address space is replaced by part of the
external parallel EEPROM in this case.
In ISA mode, the serial EEPROM is used for
configuration and IEEE Node address making it
software compatible to the SMC9000 family of
Ethernet LAN Controllers. In ISA mode, the
EEPROM is optional requiring a minimum size of
64 X 16 bit word addresses. In PCMCIA mode, the
minimum serial EEPROM (if used) size can be 64
X 16 up to 256 X 16.
This combination of internal and external attribute
memory allows the designer to reduce costs by
using a serial EEPROM device when using up to
512 bytes of “Card Information” and, if additional
memory is needed, an external EEPROM may be
used. When the SMC91C95 goes into powerdown
mode, the internal CIS data buffer RAM is re-
initialized.
The SMC91C95 generates the appropriate control
lines (nFCS and nFWE) to read and write the
Attribute memory, and it tri-states the data bus
during external Attribute Memory accesses. Note
that the parallel EEPROM is selected for the first
512 byte CIS information also in the absence of
the serial EEPROM in PCMCIA mode. Only even
locations are used.
PCMCIA Configuration Registers:
Address 8000-803Eh
The PCMCIA Configuration Registers are stored
inside the SMC91C95 above the external Attribute
Memory address space. These registers are used
to configure and control the PCMCIA related
functionality of the Ethernet and Modem functions.
These registers are eight bits wide and reside on
even locations. The SMC91C95 ignores odd
accesses to this area (ignore writes, do not drive
the bus on reads). This address offset has been
changed from prior SMC9000 PCMCIA designs to
allow a larger address range for other attribute
memory data. This data could be a larger card
information structure or a XIP data image.