SMC Networks SMC91C95 manual Pcmcia Attribute Memory Address 0- 7FFEh

	Table 6 - Powerdown Functions
	POWERDOWN	POWERDOWN	POWERS	DOES NOT
	ENTERED	EXITED		POWER DOWN
			DOWN:
(B2) Power State	When pin is low	When pin goes	Ethernet Function	Modem Function,
nWAKEUP (Pin)	and reset is	high	(Link logic	Attribute memory
	inactive		enabled)	and PCMCIA
				configuration
				Registers access,
				Link Logic
(B2) Power State	When bit is set	Write access to	Ethernet Function.	Modem function,
PWRDN bit in		I/O space or		Attribute Memory
Control Register		reset		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.

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