Datasheet

Chapter 10. Chip-Select Module 10-1
Chapter 10
Chip-Select Module
This chapter describes the MCF5407 chip-select module, including the operation and
programming model of the chip-select registers, which include the chip-select address,
mask, and control registers.
10.1 Overview
The following list summarizes the key chip-select features:
• Eight independent, user-programmable chip-select signals (CS
[7:0]) that can
interface with SRAM, PROM, EPROM, EEPROM, Flash, and peripherals
• Address masking for 64-Kbyte to 4-Gbyte memory block sizes
• Programmable wait states and port sizes
• External master access to chip selects
10.2 Chip-Select Module Signals
Table 10-1 lists signals used by the chip-select module.
Table 10-2 shows the interaction of the byte enable/byte-write enables with related signals.
Table 10-1. Chip-Select Module Signals
Signal Description
Chip Selects
(CS
[7:0])
Each CS
n can be independently programmed for an address location as well as for masking, port
size, read/write burst-capability, wait-state generation, and internal/external termination. Only CS
0
is initialized at reset when it acts as a global chip select that allows boot ROM to be at any defined
address space. Port size and termination (internal versus external) and byte enables for CS
0 are
configured by the logic levels of D[7:5] when RSTI
negates.
Output
Enable (OE
)
Interfaces to memory or to peripheral devices and enables a read transfer. It is asserted and
negated on the falling edge of the clock. OE is asserted only when one of the chip selects matches
for the current address decode.
Byte Enables/
Byte Write
Enables
(BE
[3:0]/
BWE
[3:0])
These multiplexed signals are individually programmed through the byte enable mode bit,
CSCRn[BEM], described in Section 10.4.1.3, “Chip-Select Control Registers (CSCR0–CSCR7).”
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 10-2 shows.