Geehy APM32F4xx
The Geehy APM32F4xx are Cortex-M4 based MCUs. Following information also applies for devices of the Geehy APM32A4xx family.
Supported Regions
APM32F4xx
| Flash Bank | Base address | J-Link Support | Loader | |
|---|---|---|---|---|
| Name | Size | |||
| Internal Flash | 0x08000000 | 
|
Default | Up to 1MB |
| Reserved boot area | 0x1FFFF000 | 
|
- | Up to 30KB |
| OTP area | 0x1FFF7800 |
|
- | 528 Bytes |
| Option Bytes | 0x1FFFC000 |
|
Default | 16 Bytes |
Option Byte Programming
The APM32F4 series devices provide some option bytes which allow some "permanent" configuration as well as readout protection for the device. The option bytes become effective after a reset, or, if the read protection is set while a debugger is still connected through JTAG/SWD, become effective after a power-on-reset. The sequence, to program the option bytes consists of multiple read / write accesses to special function registers of the APM32F4 MCU.
Direct programming of the option byte area is not supported by the device. Instead a special option bytes control register is used. The correct handling and remapping of the option byte area to this register is handled automatically by the J-Link.
The following table describes the structure of the option byte sector:
| Address | [15:8] | [7] | [6] | [5] | [4] | [3:2] | [1:0] |
|---|---|---|---|---|---|---|---|
| 0x1FFFC000 | RPROT | RSTSTDB | RSTSTOP | WDTSEL | --- | BORLVL | --- |
| Address | [15:12] | [11:0] | |||||
| 0x1FFFC008 | --- | NWPROT |
All other bytes of the option byte area not currently documented. Similar to other Geehy devices they seem to be used for option byte verification. This verification is done using complementary and duplicate bytes of the actual option bytes.
Any non-documented option bytes are automatically handled by the J-Link.
Writing a value of 0xFF inside RPROT will read-protect the APM32F4. In order to keep the device unprotected you have to write the key value 0xAA into RPROT.
APM32F402xB
| Flash Bank | Base address | J-Link Support | Loader | |
|---|---|---|---|---|
| Name | Size | |||
| Internal Flash | 0x08000000 |
|
Default | 128 KB |
| System Flash | 0x1FFFE400 |
|
- | 5 KB |
| Option Bytes | 0x1FFFF800 |
|
Default | 16 Bytes |
Reset
No device specific reset is necessary. The normal Cortex-M reset is performed.
See here for more information: https://wiki.segger.com/J-Link_Reset_Strategies#Type_0:_Normal
Evaluation Boards
- Geehy APM32F407VGT6 evaluation board: https://wiki.segger.com/Geehy_APM32F407VGT6
Example Application
- Geehy APM32F407VGT6 evaluation board: https://wiki.segger.com/Geehy_APM32F407VGT6#Example_Project