
MOTOROLA
Chapter 6. Memory Interface
6-45
Plugging the values into the PGMAX equation above:
PGMAX < (6600 – 213 – 2)
÷
64 = 99.7 clock cycles
The value stored in PGMAX would be 0b0110 0011 (or 99 clock cycles).
6.4.5 SDRAM Power-On Initialization
At system reset, initialization software must set up the programmable parameters in the
memory interface configuration registers (MICRs). These include the memory boundary
registers, the memory banks enable register, the memory page mode register, and the
memory control configuration registers (MCCRs). See Section 3.2.6, “Memory Interface
Configuration Registers,” for more detailed descriptions of the MICRs and MCCRs.
NOTE
The MPC106 can only support certain configurations of
parity/RMW/ECC, DRAM/EDO/SDRAM, and buffer types.
Section 6.3.3.1, “Supported Memory Interface Configurations
describes the supported memory interface configurations.
The programmable parameters relevant to the SDRAM interface are:
Memory bank starting and ending addresses (memory boundary registers)
Memory bank enables (memory bank enable register)
PGMAX—maximum activate to precharge interval (also called row active time
or t
RAS
)
SREN—self-refresh enable
RAMTYP—RAM type
PCKEN—memory interface parity checking/generation enable
Row address bit count for each bank
BUF_MODE—buffer mode
RMW_PAR—read-modify-write parity enable
BSTOPRE_U—burst to precharge interval—upper nibble
BSTOPRE_L—burst to precharge interval—lower nibble
REFREC—refresh recovery interval
RDLAT—data latency from read command
PRETOACT—precharge-to-activate interval
ACTOPRE—activate-to-precharge interval
WCBUF—memory write buffer type
RCBUF—memory read buffer type
SDMODE—SDRAM mode register
ACTORW—activate-to-read/write interval