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7.1 Overview
The external interface module (EIM) handles the interface to devices external to the
MMC2001, including generation of chip selects for external peripherals and memory.
It provides the following features:
• Four chip selects for external devices, each covering a range of 16 Mbytes
• Programmable wait-state generator for each chip select
• Selectable protection for each chip select
• Programmable data port size for each chip select
• Control for external/internal boot ROM device selection
• Bus watchdog counter for all bus cycles
• Programmable general output capability for unused chip select outputs
• Show cycles to allow internal bus cycles to be monitored externally
ADDR[31:0], R/W, TSIZ, TC
7.2 Signals
7.2.1 Address Bus
The ADDR[19:0] signals are address bus outputs used to address external devices.
MMC2001
REFERENCE MANUAL
Freescale Semiconductor, Inc.
SECTION 7
EXTERNAL INTERFACE MODULE
Timer/Reset
MOD
DATA[31:0]
TREQ, TBUSY, ABORT
TA, TEA
Figure 7-1 EIM Block Diagram
EXTERNAL INTERFACE MODULE
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Module
EIM
MOD
EB[0:1]
OE
R/W
ADDR[19:0]
DATA[15:0]
CS0
CS1
CS2
CS3
MOTOROLA
7-1
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