Syncflash Load Command Mode; Figure 24-21 Set Mode Register State Diagram; Figure 24-22 Set Mode Register Timing Diagram - Motorola DragonBall MC9328MX1 Reference Manual

SDRAM Memory Controller
(Read | Write) & SMODE = pre_cmd
(Read | Write) & SMODE = set_mode
ILLEGAL SDRAM TRANSITION
SDCLK
ADDR
RAS,
CAS,
SDWE
CSDx
DATA

24.6.6 SyncFlash Load Command Mode

SyncFlash memories extend the standard SDRAM command set to include device-specific program, erase,
and configure commands. These proprietary operations use a 3 command sequence: Load Command
register, Activate, and Read or Write. The Load Command Register serves as an "escape" code to provide
special meaning to the read or write commands which follow. The 3 command sequences must always
occur in the correct order, however any number of NOPs can be inserted between them. The Load
Command Register command is mapped to the same encoding as the SDRAM Auto-Refresh and
Self-Refresh commands.
The SyncFlash Load Command mode provides the mechanism for software to generate the first command
in the sequence. By toggling between this mode and Normal Read/Write any of the command triplets can
be generated.
An example of a configuration register read is shown in Figure 24-23. The first bus cycle places the
SDRAM Controller in the Load Command Register Mode. The following bus cycle begins the first
command of the triplet by loading the command register with the desired operation code. Because the
operation code is transferred across the address bus, either a read or write bus cycle could have been used
for this cycle. The third bus cycle returns the SDRAM Controller to the normal read/write mode. Finally,
the fourth cycle performs the actual read of the configuration register. Although not shown in the diagram,
the device configuration data would be returned across the data bus after the CAS latency had been met.
24-26
Precharge
Active
Mode Reg
Figure 24-21. Set Mode Register State Diagram
SDRAMx
REFRESH
Self-Refresh and Auto-Refresh
Figure 24-22. Set Mode Register Timing Diagram
MC9328MX1 Reference Manual
All
Set
(Read | Write) & SMODE = set_mode
t Minimum
RC
Idle
MODE
MRS
MOTOROLA