SMC Networks SMC91C95 Uživatelský manuál stáhnout pdf (Strana 21)

FUNCTIONAL DESCRIPTION

The SMC91C95 consists of an integrated Ethernet

controller mapped entirely in I/O space, as well as

support for an external Modem controller also

mapped in I/O space. In addition, PCMCIA

attribute memory space is decoded to interface an

external CIS ROM, with configuration registers as

per PCMCIA 3.X extensions implemented on-chip

in attribute space above the CIS ROM decode

area. The PCMCIA Configuration Registers are

accessible also in I/O space to allow non-PCMCIA

dual function designs.

The Ethernet controller function includes a built-in

6kbyte RAM for packet storage. This RAM buffer

is accessed by the CPU through two sequential

access regions of 3 kbytes each. The RAM access

is internally arbitrated by the SMC91C95 and

dynamically allocated between transmit and

receive packets using 256 byte pages. The

Ethernet controller functionality is identical to the

SMC91C94 except where indicated otherwise.

Table 1 - Bus Transactions in ISA Mode

A0 nSBHE D0-D7 D8-D15

8 BIT MODE

(nEN16=1)

0 X even byte -

(16 BIT=0) 1 X odd byte -

16 BIT MODE 0 0 even byte odd byte

otherwise 0 1 even byte -

1 0 - odd byte

1 1 invalid cycle

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 138 139

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SMC Networks SMC91C95 Uživatelský manuál Strana 21