MAC7200 datasheet(419/976 Pages) FREESCALE

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External Signals

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

341

•

Implements a programmable version of the MCF5407 External Bus protocol

•

Byte, word, longword, and line sized transfers

•

Programmable burst and burst-inhibited transfers selectable for each chip select and transfer

direction

•

Programmable address setup time with respect to the assertion of chip select

•

Programmable address hold time with respect to the negation of chip select and transfer direction

17.1.3

FlexBus Implementation

The FlexBus is an enhanced version of the EIM bus implemented on the MAC71xx family of devices. It

has the following special enhancements over the FlexBus controllers found on other devices:

•

Issues a bus abort for all transfers that do not hit any chip selects

17.1.4

FlexBus Memory Map Relocation

As discussed in Section 9.16, “Memory Map Relocation”, there is the possibility to relocate the base

address of the FlexBus at reset, including the option of removing it completely from the memory map (for

security reasons).

17.2

External Signals

This section describes the external signals that are involved in data transfer operations. Table 17-3

summarizes the MAC7200 FlexBus signals.

If full address decoding is done externally for anything other than an 8-bit port size, then ADDR[21:0] and

SIZE[1:0] is required, otherwise only ADDR[21:1] and BS0/BS1 are required. The basis for this required

scheme is:

•

On a 8-bit port size, only pins DATA[7:0] are available

Table 17-3. FlexBus Signal Summary

Signal Name

Direction

Description

Reset State

CS[2:0]1

1. On maskset 0M34D, output is always enabled

General purpose chip-selects

Hi-Z

ADDR[21:0]

Address bus

Hi-Z

DATA[15:0]

I/O

Data bus

Hi-Z

BWE[1:0]1

Byte Selects

Hi-Z

OE1

Output Enable

Hi-Z

R/W

Read/Write. 1 = Read, 0 = Write

Hi-Z

TBST

Burst Transfer indicator

Hi-Z

Transfer Acknowledge

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