9 SRAM CONTROLLER (SRAMC)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
9-5
Connection of External Devices and Bus Operation
9.5
Connecting External Devices
9.5.1
The following shows examples of connecting the S1C33L26 and SRAM.
S1C33L26
A[n:0]
D[7:0]
#CE
x
#RD
#WRL
SRAM
A[n:0]
I/O[7:0]
#CE
#OE
#WE
5.1.1 Example of 8-bit SRAM Connection
Figure 9.
S1C33L26
<A0 mode, 16-bit SRAM>
A[n:1]
D[15:0]
#CE
x
#RD
#WRL
#WRH
SRAM
A[n-1:0]
I/O[15:0]
#CE
#OE
#WEL
#WEH
S1C33L26
<BSL mode, 16-bit SRAM>
A[n:1]
D[15:0]
#CE
x
#RD
#WR
#BSL
#BSH
SRAM
A[n-1:0]
I/O[15:0]
#CE
#OE
#WE
#LB
#UB
5.1.2 Example of 16-bit SRAM Connection
Figure 9.
Data Configuration in Memory
9.5.2
The S1C33L26 SRAMC handles byte (8-bit), halfword (16-bit), and word (internal 32-bit) data. To access data in a
memory, addresses aligned to the boundary of the data size must be specified. Specifying other addresses generates
address misaligned exceptions.
Instructions (e.g., stack manipulating and branch instructions) that rewrite the contents of the stack pointer (SP) or
program counter (PC) forcibly alter the address specified to a boundary address to prevent address misaligned ex-
ceptions. For details of address misaligned exceptions, refer to the C33 PE Core Manual.
Table 9.5.2.1 shows where each type of data is located in a memory.
5.2.1 D
Table 9.
ata Locations in Memory
Data type
Location
Byte
Byte boundary (all addresses)
Halfword
Halfword boundary (A0 = 0)
Word
Word boundary (A[1:0] = 0b00)
All halfword and word data in a memory are accessed in little endian mode. To increase memory efficiency, try
locating the same type of data at continuous addresses to reduce blank areas created by positioning at boundary ad-
dresses as much as possible.