MCF5271 View Datasheet(PDF) - Freescale Semiconductor
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MCF5271 Datasheet PDF : 56 Pages
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Design Recommendations
Table 4. Synchronous DRAM Signal Connections
Signal
Description
SD_SRAS
SD_SCAS
DRAMW
SD_CS[1:0]
SD_CKE
BS[3:0]
CLKOUT
Synchronous row address strobe. Indicates a valid SDRAM row address is present and can be
latched by the SDRAM. SD_SRAS should be connected to the corresponding SDRAM
SD_SRAS. Do not confuse SD_SRAS with the DRAM controller’s SD_CS[1:0], which should not
be interfaced to the SDRAM SD_SRAS signals.
Synchronous column address strobe. Indicates a valid column address is present and can be
latched by the SDRAM. SD_SCAS should be connected to the corresponding signal labeled
SD_SCAS on the SDRAM.
DRAM read/write. Asserted for write operations and negated for read operations.
Row address strobe. Select each memory block of SDRAMs connected to the MCF5271. One
SD_CS signal selects one SDRAM block and connects to the corresponding CS signals.
Synchronous DRAM clock enable. Connected directly to the CKE (clock enable) signal of
SDRAMs. Enables and disables the clock internal to SDRAM. When CKE is low, memory can
enter a power-down mode where operations are suspended or they can enter self-refresh mode.
SD_CKE functionality is controlled by DCR[COC]. For designs using external multiplexing,
setting COC allows SD_CKE to provide command-bit functionality.
Column address strobe. For synchronous operation, BS[3:0] function as byte enables to the
SDRAMs. They connect to the DQM signals (or mask qualifiers) of the SDRAMs.
Bus clock output. Connects to the CLK input of SDRAMs.
6.7.1.2 Address Multiplexing
Table 5 shows the generic address multiplexing scheme for SDRAM configurations. All possible address
connection configurations can be derived from this table.
Table 5. Generic Address Multiplexing Scheme
Address Pin Row Address Column Address
Notes Related to Port Sizes
17
17
16
16
15
15
14
14
13
13
12
12
11
11
10
10
9
9
17
17
18
18
19
19
20
20
0
8-bit port only
1
8- and 16-bit ports only
2
3
4
5
6
7
8
16
32-bit port only
17
16-bit port only or 32-bit port with only 8
column address lines
18
16-bit port only when at least 9 column
address lines are used
19
MCF5271 Integrated Microprocessor Hardware Specification, Rev. 1.2
Freescale Semiconductor
21
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