10 SDRAM CONTROLLER (SDRAMC)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
10-9
SDRAM Commands
10.5.2
The SDRAM is controlled by commands that are comprised of a combination of high or low logic level signals.
The table below lists the commands output by the SDRAMC.
5.2.1 List of the Supported SDRAM Commands
Table 10.
Command
SDCKE
DQM
(DQMH/L)
SDBA[1:0]
SDA10
SDA[12:11]
SDA[9:0]
#SDCS
#SDRAS #SDCAS #SDWE
Deselect
H
–
–
–
–
H
–
–
–
Bank Active (ACTV)
H
–
V
V
V
L
L
H
H
Specified Bank Precharge (PRE)
H
–
V
L
–
L
L
H
L
Precharge All banks (PALL)
H
–
–
H
–
L
L
H
L
Write (WRIT)
H
–
V
L
V
L
H
L
L
Read (READ)
H
–
V
L
V
L
H
L
H
Mode Register Set (MRS)
H
–
–
V
V
L
L
L
L
No Operation (NOP)
H
–
–
–
–
L
H
H
H
Auto-Refresh (REF)
H
–
–
–
–
L
L
L
H
Self-Refresh (SELF)
H
→
L
–
–
–
–
L
L
L
H
End Self-Refresh
L
→
H
–
–
–
–
H
–
–
–
Data Write/Output Enable
H
L
–
–
–
–
–
–
–
Data Write/Output Disable
H
H
–
–
–
–
–
–
–
V = Valid, – = Optional/Unknown, L = Low level, H = High level
Because all of these commands are output by the SDRAM controller as necessary, they do not need to be controlled
by the user program, except for initializing the SDRAM.
SDRAM Bus Operations
10.5.3
The external data bus of the S1C33L26 is sized to 16 bits. Depending on the device size and data size of the instruc-
tion executed, two or more bus operations may occur. The table below shows bus operations in the SDRAM area.
5.3.1 Bus Operations
Table 10.
Device
size
Data size
R/W
A1
A0
Little endian
Access
count
Valid
signal
D[15:8]
pins
D[7:0]
pins
16 bits
Byte
W
*
0
DQML
–
D[7:0]
1
*
1
DQMH
D[7:0]
–
1
R
*
0
DQMH/L
–
D[7:0]
1
*
1
D[7:0]
–
1
Halfword
W
*
*
DQMH/L
D[15:0]
1
R
*
*
DQMH/L
D[15:0]
1
Word
W
0
*
DQMH/L
D[15:0]
1st
1
*
D[31:16]
2nd
R
0
*
DQMH/L
D[15:0]
1st
1
*
D[31:16]
2nd