6-22
MPC8240 Integrated Processor User’s Manual
SDRAM Interface Operation
The value of the above six parameters, (in whole clock cycles) must be set by boot code at
system start-up and kept in the MPC8240 configuration register space.
The following figures show SDRAM timing for various types of accesses. Figure 6-8 shows
a single-beat read operation.
Table 6-11. SDRAM Interface Timing Intervals
Timing Intervals
Definition
RDLAT
The number of clock cycles from the read column command until the first data beat is
available on the internal processor core data bus.
RDLAT = SDRAM CAS l buffer mode delay + delay due to REGDIMM value. The
value of RDLAT should be additionally increased by one if MCCR3[REGDIMM] = 1.
RDLAT Mode
MCCR3[REGDIMM]
0
1
Flow through
CL
–
Registered
CL + 1
CL + 2
In-line ECC
CL + 2
CL + 3
REFREC
The number of clock cycles from the refresh command until an activate command is
allowed. This can be calculated by referring to the AC specification of the SDRAM device.
The AC specification indicates a minimum refresh to activate interval in nanoseconds.
ACTORW
The number of clock cycles from an activate command until a read or write command is
allowed. This interval will be listed (nS) in the AC specifications of the user’s SDRAM.
ACTOPRE
The number of clock cycles from an activate command until a precharge command is
allowed. This interval will be listed (nS) in the AC specifications of the user’s SDRAM.
PRETOACT
The number of clock cycles from a precharge command until an activate command is
allowed. This interval will be listed (nS) in the AC specifications of the user’s SDRAM.
BSTOPRE
The number of clock cycles to maintain a page open after an access. A subsequent
access can generate a page hit during this interval. A page hit reloads the BSTOPRE
counter. When the interval expires, a precharge is issued to the page.
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 ...