3 MEMORY MAP
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
3-5
Memory access cycle
Number of access cycles
Single byte
Single half-word
Single word
Successive
address
Burst
access
Area 6 register (8-bit) read
6
9
15
–
–
Area 6 register (8-bit) write
3
6
12
–
–
Area 6 register (16-bit) read
6
6
9
–
–
Area 6 register (16-bit) write
3
3
6
–
–
Area 6 register (32-bit) read
6
6
6
–
–
Area 6 register (32-bit) write
3
3
3
–
–
External SRAM/ROM
(8-bit) read/write
4 + S + W + H 6 + (S + W + H)
×
2 8 + (S + W + H)
×
4
–
(
*
3)
External SRAM/ROM
(16-bit) read/write
4 + S + W + H
4 + S + W + H
6 + (S + W + H)
×
2
–
(
*
3)
W: Number of WAIT cycles (0 min.) S: Number of SETUP cycles (1 min.) H: Number of HOLD cycles (1 min.)
(Note)
*
1: 1 cycle if there is an idle cycle inserted before starting a successive read. Otherwise, just reduce the number of
single access cycle by 1.
*
2: The cache controller does not support IVRAM, so burst read will be issued by the LCDC when IVRAM is used as
a VRAM or by the DMAC when used as a DMA control table. Add (1 + W) cycles to single word access cycles.
*
3: Burst access can be regarded as 4 or 8 single word access cycles. However, refer to item (2) below for the exter-
nal SRAM/ROM access cycle when the SDRAMC is enabled and it is in self-refresh mode.
(2) External SRAM access rate while the SDRAM is in self-refresh status
Table 3.8.2 lists the number of external SRAM access cycles when SDON/SDRAMC_INIT register is set to 1
(SDRAMC enabled) and SELEN/SDRAMC_REF register is set to 1 (self-refresh enabled).
When SDON is set to 0 (SDRAMC disabled) or SELEN is set to 0 (self-refresh disabled), the SRAM will be
accessed according to the setup, hold, and wait cycle conditions set using the SRAMC register.
The S1C33L26 is designed under the assumption that the CPU is set in HALT status and the LCDC only is ac-
tive while the SDRAM is placed into self-refresh mode.
The SDRAMC should be disabled by setting SDON to 0 if no SDRAM is used.
The T80NS[3:0]/SDRAMC_CFG register value (t
RC
, t
RFC
, t
XSR
) should be set to 0x0, 0x4, 0x8, or 0xc.
SDCLK
#CE10
#RD
1s
1s: 1st word setup cycle, 1r: 1st word read cycle, 1h: 1st word hold cycle
2s: 2nd word setup cycle, 2r: 2nd word read cycle, 2h: 2nd word hold cycle
1st word
#CE10 high period
2nd word
1r 1h 2s 2r 2h
(Setting example: T80NS[3:0] = 0xe, CE10SETUP[1:0] = 0x0, CE10HOLD[1:0] = 0x0, CE10WAIT[3:0] = 0x0)
8.1 SRAM Access Cycle during SDRAM Self-Refresh
Figure 3.
8.2 SRAM Access Cycle during SDRAM Self-Refresh
Table 3.
(Condition: No other access sources, Unit: cycle)
SDRAMC
SRAMC
#CE10
high
period
1st word
2nd word
T80NS
[3:0]
CE
x
SETUP
[1:0]
CE
x
WAIT
[3:0]
CE
x
HOLD
[1:0]
Setup
cycle
Read
cycle
Hold
cycle
Setup
cycle
Read
cycle
Hold
cycle
0x0
0x0
W
H
5
1
W + 1
H + 1
1
W + 1
H + 1
0x1
0x0
W
H
5
4 (
*
3)
W + 1
H + 1
1
W + 1
H + 1
0x2
0x0
W
H
5
3 (
*
3)
W + 1
H + 1
1
W + 1
H + 1
0x3
0x0
W
H
5
2 (
*
3)
W + 1
H + 1
1
W + 1
H + 1
0x4
0x0
W
H
5
1
W + 1
H + 1
1
W + 1
H + 1
0x5
0x0
W
H
6 (
*
1)
4 (
*
3)
W + 1
H + 1
1
W + 1
H + 1
0x6
0x0
W
H
7 (
*
1)
3 (
*
3)
W + 1
H + 1
1
W + 1
H + 1
0x7
0x0
W
H
8 (
*
1)
2 (
*
3)
W + 1
H + 1
1
W + 1
H + 1
0x8
0x0
W
H
9 (
*
1)
1
W + 1
H + 1
1
W + 1
H + 1
0x9
0x0
W
H
10 (
*
1)
4 (
*
3)
W + 1
H + 1
1
W + 1
H + 1
0xa
0x0
W
H
11 (
*
1)
3 (
*
3)
W + 1
H + 1
1
W + 1
H + 1