Internal VS External Attribute Memory Map

The Internal VS External EPROM attribute memory decodes are shown below. This allows the designer to not require an external EPROM device if the single or multi-function PCMCIA card needs less than 512 bytes of configuration information. As can be seen in the map, if 512 bytes of CIS or less is required, the nFCS and

nFWE

output

pins

of

the

SMC91C95 need not be used (if serial EEPROM is being used). Internal to the SMC91C95, the memory addressing logic will allow byte or word on odd byte address access (A0=1), the SMC91C95 will generate an arbitrary value of zero (0) since the PCMCIA specification states that the high byte of a word access in attribute memory is a don’t care. This allows backward compatibility to 8 bit hosts.

Table 7 - Attribute Memory Address Using Serial EEPROM

ATTRIBUTE

EXTERNAL EPROM

INTERNAL SRAM

CONFIGURATION

MEMORYADDRESS

STORE

STORE (512 BYTES)

REGISTERS

 

 

 

 

 

0 - 3FEh

 

X

 

 

 

 

 

 

400h-7FFEh

X

 

 

 

 

 

 

 

8000h - 803Eh

 

 

X

 

 

 

 

 

Table 8 - Attribute Memory Address without Serial EEPROM

 

 

 

 

 

ATTRIBUTE

 

EXTERNAL EPROM

INTERNAL SRAM

CONFIGURATION

MEMORYADDRESS

 

STORE

STORE (512 BYTES)

REGISTERS

 

 

 

 

 

0 - 7FFEh

 

X

 

 

 

 

 

 

 

8000h - 803Eh

 

 

 

X

 

 

 

 

 

36

Page 36
Image 36
SMC Networks SMC91C95 manual Attribute Memory Address Using Serial Eeprom, 7FFEh 8000h 803Eh