9 SRAM CONTROLLER (SRAMC)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
9-3
Chip Enable Signals
9.4.1
The SRAMC provides maximum 26 bits of an external address bus, 16 bits of an external data bus, and 6 chip-
enable pins (#CE4, #CE5, #CE7 to #CE10), allowing access to a maximum 336M-byte address space.
Two or more areas are assigned to each chip-enable signal. Table 9.4.1.1 shows the relationship between the chip-
enable pins and corresponding areas.
4.1.1 Chip Enable Pins and Corresponding Areas
Table 9.
#CE pin
Corresponding area
Available area capacity for a series of adjacent addresses
Area
Capacity
Area
Capacity
Area
Capacity
#CE4
Areas 4 and 14
Area 4
1MB
Area 14
16MB
–
–
#CE5
Areas 5, 15, and 16
Area 5
1MB
Areas 15 + 16
64MB
–
–
#CE7
Areas 7 and 19
Area 7
2MB
Area 19
64MB
–
–
#CE8
Areas 8 and 21
Area 8
2MB
Area 21
64MB
–
–
#CE9
Areas 9 and 22
Area 9
4MB
Area 22
64MB
–
–
#CE10 Areas 10, 13, and 20
Area 10
4MB
Area 13
16MB
Area 20
64MB
The #CE
x
signal becomes active when an address in any corresponding area is accessed.
Area Condition Settings
9.4.2
Bus access conditions can be set by area for each #CE
x
signal. Therefore, the same conditions are set for two or
more areas accommodated by the respective #CE
x
signals.
This section describes the parameters to be set individually for each #CE
x
area and the relevant control bits.
The SRAMC control registers are initialized by an initial reset. These registers should be set up in software to suit
the external device configuration or specification as required.
Note: Letter ‘
x
’ in the control bit and #CE names denotes a #CE area number (4, 5, or 7 to 10).
Endian mode
The S1C33L26 supports little endian mode only.
Device type
The device size can be selected from 8 bits and 16 bits. Additionally, for a 16-bit device, the device type can
also be selected from the A0 (default) or BSL modes.
For selection, use CE
x
TYPE[1:0]/SRAMC_TYPE register.
4.2.1 Device Type Selections
Table 9.
CE
x
TYPE[1:0]
Device type
Pins to be used
0x3–0x2
8-bit device
A[25:0], D[7:0], #CE
x
, #RD, #WRL
0x1
16-bit BSL device A[25:1], D[15:0], #CE
x
, #RD, #WRL, #BSL(A0), #BSH
0x0
16-bit A0 device
A[25:1], D[15:0], #CE
x
, #RD, #WRL, #WRH
(Default: 0x0)
#CE setup time
The setup time for #CE
x
signals (from a #CE
x
falling edge to the read/write signal falling edge) can be set to
within the range from 1 to 4 cycles. Use CE
x
SETUP[1:0] in the SRAMC_TMG47 and SRAMC_TMG810 reg-
isters for settings.
4.2.2 #CE Setup Time Settings
Table 9.
CE
x
SETUP[1:0]
Setup time
0x3
4 cycles
0x2
3 cycles
0x1
2 cycles
0x0
1 cycle
(Default: 0x3)