Chapter 6. MPC8240 Memory Interface
6-55
FPM or EDO DRAM Interface Operation
The data path between the internal processor bus to the external memory bus in
flow-through mode is shown in Figure 6-34. The flow-through mode is the default data bus
buffering mode for the MPC8240.
Note that in-line ECC is not available with FPM or EDO DRAM.
Figure 6-34. FPM-EDO Flow-through Memory Interface
6.3.4 FPM or EDO DRAM Initialization
At system reset, the main memory is inactive. When the reset signals (HRST_CPU and
HRST_CTRL) are negated, the MEMGO bit is cleared to zero (0) which turns off the
memory controller. The processor 5core starts fetching boot code from ROM (local or PCI).
For systems containing FPM or EDO DRAM, the boot code must set the MPC8240
configuration bit RAMTYP = 1.
Additionally, all other MPC8240 configuration registers relevant to DRAM must be
initialized. Table 6-21 shows the register fields in the memory interface configuration
registers (MICRs) and the memory control configuration registers (MCCRs).
Table 6-21. Memory Interface Configuration Register Fields
Register Field
Description
Configuration
Register (and offset)
RAM_TYPE
SDRAM, FPM, or EDO DRAM
MCCR1 @ <F0>
Memory Bank
Start and End Addresses
MICR @ <80>–<9C>
Memory Bank Enables
MICR @ <A0>
Row Address Bits For Each Bank
MCCR1 @ <F0>
PCKEN
Parity check enable
MCCR1 @ <F0>
SREN
Self refresh enable
MCCR1 @ <F0>
REFINT
Interval between refreshes
MCCR2 @ <F4>
RP1
RAS precharge interval
MCCR3 @ <F8>
RCD2
RAS to CAS delay
MCCR3 @ <F8>
CAS3
CAS assertion interval for first data beat
MCCR3 @ <F8>
CP4
CAS precharge interval
MCCR3 @ <F8>
CAS5
CAS assertion interval for page mode data beats
MCCR3 @ <F8>
RAS6P
RAS assertion interval for CBR refresh
MCCR3 @ <F8>
RMW_PAR
Read modify write parity
MCCR2 @ <F4>
DRAM data path
Processor data from DRAM
signals
Processor data to DRAM
Output enable
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 ...