AT40KAL datasheet(6/38 Pages) ATMEL

6 / 38 page

AT40KAL

4263B–AERO–06/03

The Busing Network

Figure 3 on page 7 depicts one of five identical busing planes. Each plane has three bus

resources: a local-bus resource (the middle bus) and two express-bus (both sides)

resources. Bus resources are connected via repeaters. Each repeater has connections

to two adjacent local-bus segments and two express-bus segments. Each local-bus

segment spans four cells and connects to consecutive repeaters. Each express-bus

segment spans eight cells and “leapfrogs” or bypasses a repeater. Repeaters regener-

ate signals and can connect any bus to any other bus (all pathways are legal) on the

same plane. Although not shown, a local bus can bypass a repeater via a programma-

ble pass gate allowing long on-chip tri-state buses to be created. Local/Local turns are

implemented through pass gates in the cell-bus interface (see following page).

Express/Express turns are implemented through separate pass gates distributed

throughout the array.

Some of the bus resource on the AT40KAL is used as a dual-function resource. Table 2

shows which buses are used in a dual-function mode and which bus plane is used. The

AT40KAL software tools are designed to accommodate dual-function buses in an effi-

cient manner.

Table 2. Dual-function Buses

Function

Type

Plane(s)

Direction

Comments

Cell Output Enable

Local

Horizontal and

Vertical

RAM Output Enable

Express

Vertical

Bus full length at array edge

Bus in first column to left of RAM block

RAM Write Enable

Express

Vertical

Bus full length at array edge

Bus in first column to left of RAM block

RAM Address

Express

1 - 5

Vertical

Buses full length at array edge

Buses in second column to left of RAM block

RAM Data In

Local

Horizontal

RAM Data Out

Local

Horizontal

Clocking

Express

Vertical

Bus half length at array edge

Set/Reset

Express

Vertical

Bus half length at array edge

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