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Chapter 12
Chip Select Module
This chapter describes the MCF5282 chip select module, including the operation and
programming model of the chip select registers, which include the chip select address,
mask, and control registers.
Unless otherwise noted, in this chapter, "clock" refers to the
CLKOUT used for the bus.
12.1 Overview
The following list summarizes the key chip select features:
• Up to seven independent, user-programmable chip select signals (CS[6:0]) that can
interface with external SRAM, PROM, EPROM, EEPROM, Flash, and peripherals
• Address masking for 64-Kbyte to 4-Gbyte memory block sizes
12.2 Chip Select Module Signals
Table 12-1 lists signals used by the chip select module.
Signal
Chip Selects
Each CSn can be independently programmed for an address location as well as for masking, port
(CS[6:0])
size, read/write burst capability, wait-state generation, and internal/external termination. Only CS0 is
initialized at reset and may act as an external boot chip select to allow boot ROM to be at an external
address space. Port size for CS0 is configured by the logic levels of D[19:18] when RSTO negates
and RCON is asserted.
Output Enable
Interfaces to memory or to peripheral devices and enables a read transfer. It is asserted and negated
(OE)
on the falling edge of the clock. OE is asserted only when one of the chip selects matches for the
current address decode.
Byte Strobes
These signals are individually programmed through the byte-enable mode bit, CSCRn[BEM],
BS[3:0]
described in Section 12.4.1.3.
These generated signals provide byte data select signals, which are decoded from the transfer size,
A1, and A0 signals in addition to the programmed port size and burstability of the memory accessed,
as Table 12-2 shows.
MOTOROLA
NOTE
Table 12-1. Chip Select Module Signals
Chapter 12. Chip Select Module
Description
12-1
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