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MPC8240 Integrated Processor User’s Manual
Memory Control Configuration Registers
Table 4-41. Bit Settings for MCCR4—0xFC
Bits
Name
Reset
Value
Description
31–28 PRETOACT
0000
Precharge to activate interval. For SDRAM only. These bits control the number
of clock cycles from an SDRAM-precharge command until an SDRAM-activate
command is allowed. See Section 6.2.4, “SDRAM Power-On Initialization,” for
more information.
0001 1 clock
0010 2 clocks
0011 3 clocks
...
...
1111 15 clocks
0000 16 clocks
27–24
ACTOPRE
0000
Activate to precharge interval. For SDRAM only. These bits control the number
of clock cycles from an SDRAM-activate command until an SDRAM-precharge
command is allowed. See Section 6.2.4, “SDRAM Power-On Initialization,” for
more information.
0001 1 clock
0010 2 clocks
0011 3 clocks
...
...
1111 15 clocks
0000 16 clocks
23
WMODE
0
Length of burst for 32-bit data. Applies to 32-bit data path mode only.
Determines whether the burst ROMs can accept eight beats in a burst or only
four. In 32-bit data path mode, burst transactions require data beats. If the burst
ROM can only accept four beats per burst, the memory controller must perform
two transactions to the ROM.
0 Four beats per burst (default)
1 Eight beats per burst
22
BUF_TYPE[0]
0
Most significant bit of the memory data bus buffer type field. BUF_TYPE[0] is
used with bit 20 below (BUF_TYPE[1]) to configure the internal memory data
path buffering scheme as follows:
BUF_TYPE[0–1]:
00 Flow through buffer mode (default)
01 Registered buffer mode
10 In-line buffer mode; SDRAM only
11 Reserved
The MPC8240 must be configured for in-line buffer mode in order to use the
in-line ECC/parity logic for SDRAM. The in-line ECC and parity hardware allow
the MPC8240 to check/generate parity on the internal peripheral logic bus and
check/correct/generate ECC or parity on the external SDRAM memory bus. See
Section 6.2.3, “SDRAM Memory Data Interface,” and Section 6.3.3,
“FPM or EDO Memory Data Interface,” for more information.
21
—
0
Reserved
Summary of Contents for MPC8240
Page 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Page 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Page 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Page 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Page 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Page 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Page 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Page 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Page 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Page 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Page 516: ...16 14 Watchpoint Trigger Applications ...
Page 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Page 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Page 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...