9 SRAM CONTROLLER (SRAMC)
9-6
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
External Bus Operation
9.5.3
The internal data bus size in the S1C33L26 is 32 bits. Note, however, that it has 16 external bus pins D[15:0].
Depending on the device size and data size of the instruction executed, two or more bus operations may occur.
Table 9.5.3.1 shows bus operations in A0 and BSL modes.
For details on how to connect memory, see Section 9.5.1, “Connecting External Devices.”
5.3.1 Bus Operations
Table 9.
Device
size
Data size
R/W
A1
A0
A0 mode
BSL mode
Access
count
Valid
signal
D[15:8]
pins
D[7:0]
pins
Valid
signal
D[15:8]
pins
D[7:0]
pins
8 bits
Byte
W
*
*
#WRL
–
D[7:0]
–
–
–
1
R
*
*
#RD
–
D[7:0]
–
–
–
1
Halfword
W
*
0
#WRL
–
D[7:0]
–
–
–
1st
*
1
–
D[15:8]
–
–
2nd
R
*
0
#RD
–
D[7:0]
–
–
–
1st
*
1
–
D[15:8]
–
–
2nd
Word
W
0
0
#WRL
–
D[7:0]
–
–
–
1st
0
1
–
D[15:8]
–
–
2nd
1
0
–
D[23:16]
–
–
3rd
1
1
–
D[31:24]
–
–
4th
R
0
0
#RD
–
D[7:0]
–
–
–
1st
0
1
–
D[15:8]
–
–
2nd
1
0
–
D[23:16]
–
–
3rd
1
1
–
D[31:24]
–
–
4th
16 bits
Byte
W
*
0
#WRL
–
D[7:0]
#WR
#BSL
–
D[7:0]
1
*
1
#WRH
D[7:0]
–
#WR
#BSH
D[7:0]
–
1
R
*
0
#RD
–
D[7:0]
#RD
#BSL
–
D[7:0]
1
*
1
D[7:0]
–
#RD
#BSH
D[7:0]
–
1
Halfword
W
*
0
#WRH
#WRL
D[15:0]
#WR
#BSH
#BSL
D[15:0]
1
R
*
0
#RD
D[15:0]
#RD
#BSH
#BSL
D[15:0]
1
Word
W
0
0
#WRH
#WRL
D[15:0]
#WR
#BSH
#BSL
D[15:0]
1st
1
0
D[31:16]
D[31:16]
2nd
R
0
0
#RD
D[15:0]
#RD
#BSH
#BSL
D[15:0]
1st
1
0
D[31:16]
D[31:16]
2nd