MMC2001
EXTERNAL INTERFACE MODULE
MOTOROLA
REFERENCE MANUAL
7-3
If MOD is driven to a logic-low level four LOW_REFCLK clock cycles before RSTOUT
negation, and the CSEN0 bit is enabled (the default state on reset), then the internal
ROM is disabled, and CS0 is asserted for the first CPU access. The internal ROM is
disabled for the first CPU access only and is available for subsequent accesses. The
CS0 access uses default values of 15 wait states and a 16-bit port size.
7.2.6.2 Chip Select 1–2 (CS[1:2])
These active-low output signals are asserted based on a decode of bits ADDR[31:24]
of the access address. When disabled, these pins can be used as programmable
general-purpose outputs.
7.2.6.3 Chip Select 3 (CS3)
This active-high output signal is asserted based on a decode of the internal address
bus bits ADDR[31:24] of the access address. When disabled, this pin can be used as
a programmable general-purpose output.
7.3 Chip-Select Address Range
Table 7-1 specifies the address range for each chip select output.
7.4 EIM Interface Example
Figure 7-2 shows an example of an EIM interface to memory and peripherals.
Table 7-1 Chip Select Address Range
CSENx
ADDR[31:24]
Chip Select
Typical Use
Cleared
—
Inactive
—
Set
00101101
CS0 Flash
Set
00101111
CS1
SRAM
Set
00101110
CS2
Spare
Set
00101100
CS3
LCD
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