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MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
8-1
Chapter 8
Chip Select Module
This chapter describes the chip select module, including the chip select registers, the configuration and
behavior of the chip select signals, and the global chip select functions.
8.1
Overview
The chip select module provides user-programmable control of the eight chip select and four byte strobe
outputs. This subsection describes the operation and programming model of the chip select registers,
including the chip select base and option registers.
8.1.1
Features
The following list summarizes the key chip select features:
•
Eight dedicated programmable chip selects
•
Address masking for memory block sizes from 4 Kbytes to 2 Gbytes
•
Programmable wait states and port sizes
•
Programmable address setup
•
Programmable address hold for read and write
•
SDRAM controller interface supported with CS7/SDCS
•
Global chip select functionality
8.1.2
Chip Select Usage
Each of the eight chip selects, CS0–CS7, is configurable for external SRAM, ROM, and peripherals. CS0
is used to access external boot ROM and is enabled after a reset. The data bus width of the external ROM
must be configured at reset by having appropriate pull-down resistors on QSPI_CLK/BUSW1 and
QSPI_CS0/BUSW0. At reset these two signals replace the bus width field in the chip select 0 base register
(CSBR0[BW]).
CS7 must be used for enabling an external SDRAM array. In this mode, it is referred to as SDCS.
NOTE
A detailed description of each bus access type supported by the MCF5272
device is given in