P i n o u t d e t a i l t a b l e s a n d s i g n a l d e s c r i p t i o n s

Mnemonic

Signal

Description

 

 

 

TA_

Transfer acknowledge

Indicates the end of the current system bus

 

 

memory cycle. This signal is driven to 1 prior to

 

 

tri-stating its driver.

 

 

TA_ is bi-directional.

 

 

 

TEA_

Transfer error

Indicates an error termination or burst cycle

 

acknowledge

termination:

 

 

In conjunction with TA_ to signal the end of a

 

 

burst cycle.

 

 

Independently of TA_ to signal that an error

 

 

occurred during the current bus cycle. TEA_

 

 

terminates the current burst cycle.

 

 

This signal is driven to 1 prior to tri-stating its

 

 

driver.

 

 

TEA_ is bi-directional. The NS7520 or the external

 

 

peripheral can drive this signal.

 

 

 

RW_

Read/write indicator

Indicates the direction of the system bus memory

 

 

cycle. RW_ high indicates a read operation; RW_

 

 

low indicates a write operation. The RW_ signal is

 

 

bi-directional.

 

 

 

BR_

Bus request

NO CONNECT

 

 

 

BG_

Bus grant

NO CONNECT

 

 

 

BUSY_

Bus busy

NO CONNECT

 

 

 

Table 3: System bus interface signal description

Chip select controller

The NS7520 supports five unique chip select configurations:

Symbol

Pin

I/O

OD

Description

 

 

 

 

 

CS4_

B4

O

4

Chip select/DRAM RAS_

 

 

 

 

 

CS3_

A4

O

4

Chip select/DRAM RAS_

 

 

 

 

 

CS2_

C5

O

4

Chip select/DRAM RAS_

 

 

 

 

 

CS1_

B5

O

4

Chip select/DRAM RAS_

 

 

 

 

 

Table 4: Chip select controller pinout

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Image 30
Digi NS7520 manual Chip select controller pinout, Busy