GD32F403xx User Manual
34
◼
byte_offset is the number of the byte in the bit-band region that contains the targeted bit.
◼
bit_number is the bit position (0-7) of the targeted bit.
For example, to access bit 7 of address 0x2000 0200, the bit-band alias is:
bit_word_addr = 0x2200 0000 + (0x200 * 32)+ (7 * 4)= 0x2200 401C (1-2)
Writing to address 0x2200 401C will cause bit 7 of address 0x2000 0200 change while a read
to address 0x2200 401C will return 0x01 or 0x00 according to the value of bit 7 at the SRAM
address 0x2000 0200.
1.3.2.
On-chip SRAM memory
The GD32F403xx series of devices contain up to 128 KB of on-chip SRAM which starts at
the address 0x2000 0000. It supports byte, half-word (16 bits), and word (32 bits) accesses.
1.3.3.
On-chip flash memory overview
The devices provide high density on-chip flash memory, which is organized as follows:
-
Up to 3072KB of main flash memory.
-
Up to 18KB of information blocks for the boot loader.
-
Option bytes to configure the device.
Ref er to
Chapter for more details.
1.4.
Boot configuration
The GD32F403xx devices provide three kinds of boot sources which can be selected by the
BOOT0 and BOOT1 pins. The details are shown in the following table. The value on the two
pins is latched on the 4th rising edge of CK_SYS af ter a reset. It is up to the user to set the
BOOT0 and BOOT1 pins after a power-on reset or a system reset to select the required boot
source. Once the two pins have been sampled, they are f ree and can be used f or other
purposes.
Table 1-3. Boot modes
Selected boot source
Boot mode selection pins
Boot1
Boot0
Main Flash Memory
x
0
Boot loader
0
1
On-chip SRAM
1
1
Af ter power-on sequence or a system reset, the Arm
®
Cortex
®
-M4 processor fetches the top-
of -stack value f rom address 0x0000 0000 and the base address of boot code f rom 0x0000
0004 in sequence. Then, it starts executing code from the base address of boot code.
Due to the selected boot source, either the main f lash memory (original memory space
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