APPENDIX D BOOT
AP-D-2
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
NOR Flash/External ROM Boot Sequence
D.2.2
Figure D.2.2.1 shows the NOR Flash/external ROM boot flowchart.
START
Initializes TTBR (0x20000000)
Jumps to reset vector
Enables access to Area 10 in default
settings (boot disabled)
Configures Area 10 for 8-bit devices
Loads reset vector
LSB of 0x20000000
0
1
2.2.1 NOR Flash/External ROM Boot Flowchart
Figure D.
(1) When the BOOT pin is set to 0 at power-on or reset, the NOR Flash/external ROM boot sequence is executed.
(2) Checks the LSB of the reset vector written at address 0x20000000.
(3) Sets the #CE10 area device size to 8 bits if the LSB of the reset vector is 1.
Leaves it unchanged (16 bits) if the LSB of the reset vector is 0.
(4) Reads the reset vector again and jumps to that address.
Figures D.2.2.2 and D.2.2.3 show 16-bit and 8-bit NOR Flash boot sequences.
#CE10
#RD
A[25:0]
D[15:0]
C00000
C00002
20000000
P[15:0]
P[31:16]
20000000
20000002
P[15:0]
P[31:16]
P
P + 2
P[15:0]
Dummy
read
Reset vector
read
Jump to P
LSB
check
Bus size
configuration
2.2.2 16-bit NOR Flash Boot
Figure D.
#CE10
#RD
A[25:0]
D[7:0]
C00000
C00002
20000000
P[7:0]
P[23:16]
20000000
20000003
P[7:0]
20000001
P[15:8]
20000002
P[23:16]
P[31:24]
P
P + 2
P[7:0]
Dummy
read
Reset vector
read
Jump to P
LSB
check
Bus size
configuration
2.2.3 8-bit NOR Flash Boot
Figure D.
Reset Vector for NOR Flash/External ROM Boot
D.2.3
To boot up the system from a 16-bit NOR Flash/external ROM, write a reset vector in which the LSB is set to 0 to
address 0x20000000.
To boot up the system from an 8-bit NOR Flash/external ROM, write a reset vector in which the LSB is set to 1 to
address 0x20000000.