SC220 datasheet(14/34 Pages) ZARLINK

14 / 34 page

PRELIMINARY

INFORMATION

XpressFlow-2020 Series –

SC220

Ethernet Switch Chipset

XpressFlow Engine

Rev. 4.5 – February

1999

2.2

Local Memory (Control Buffer Memory) Interface

t Uses industry standard Synchronous Burst SRAM (Pipe-lined Mode)

◊ Supports 64k x 32, 128k x 32, or 256k x 32 chips up to maximum 2M bytes

t Provides 4 individual Byte Write Enable controls

t Supports back to back Read or Write operations

2.2.1

Pin Description

Symbol

Type

Name & Functions

L_D[31:0]

TTL

I/O-TS

Local Memory Data Bus Bit [31:0] – a 32-bit synchronous data bus.

L_A[18:2]

CMOS

Output

Local Memory Address Bus Bit [18:2] – Bit [17:2] of a synchronous ad-

dress bus. The memory address is sampled when L_CS# is enabled

and L_ADSC# is asserted.

L_A[19] /

L_WE[3]#

CMOS

Output

Local Memory Address Bus Bit [19] or Local Memory Write Chip Select

[3] – Depends on memory configuration, this pin can be used as the

Local Memory Address Bit [19] or as the Local Memory Write Chip

Select [3].

L_WE[2:0]#

CMOS

Output

Local Memory Write Chip Select [2:0] – allows up to write one of the 4

banks of memory.

L_OE[3:0]#

CMOS

Output

Local Memory Read Chip Select [3:0] – allows up to read one of the 4

banks of memory.

L_BWE[3:0]#

CMOS

Output

Local Memory Byte Write Enable [3:0] – use to write individual bytes.

L_ADSC#

CMOS

Output

Local Memory Controller Address Status – to load a new address.

L_CLK

CMOS

Output

Local Memory Clock – a synchronous clock to memory devices.

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