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Change to max 100 KB app with 28 KB stack

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Daniel Lublin 2022-10-31 15:02:48 +01:00
parent fdda69745e
commit a14662c622
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5 changed files with 24 additions and 20 deletions
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10
doc/system_description/software.md
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@ -63,7 +63,9 @@ between the host and the device.
## Firmware
The device has 128 KB RAM. The current firmware loads the app at the
upper 64 KB. The lower 64 KB is currently set up as stack for the app.
upper 100 KB. The lower 28 KB is set up as stack for the app. A
smaller app that wants a larger stack could relocate itself on
startup.
The firmware is part of FPGA bitstream (ROM), and is loaded at
`0x0000_0000`.
@ -73,7 +75,7 @@ The firmware is part of FPGA bitstream (ROM), and is loaded at
The PicoRV32 starts executing at `0x0000_0000`. Our firmware starts at
`_start` from `start.S` which initializes the `.data`, and `.bss` at
`0x4000_0000` and upwards. A stack is also initialized, starting at
0x4000_fff0 and downwards. When the initialization is finished, the
0x4000_6ff0 and downwards. When the initialization is finished, the
firmware waits for incoming commands from the host, by busy-polling
the `UART_RX_{STATUS,DATA}` registers. When a complete command is
read, the firmware executes the command.
@ -355,8 +357,8 @@ Assigned core prefixes:
| | | | | | | returns 0 if device is in firmware mode, 0xffffffff if in app mode. |
| `LED` | w | w | 1B | u8 | | |
| `GPIO` | | | | | | |
| `APP_ADDR` | r/w | r | 4B | u32 | | Application address (0x4000_0000) |
| `APP_SIZE` | r/w | r | 4B | u32 | | Application size |
| `APP_ADDR` | r/w | r | 4B | u32 | | Firmware stores app load address here, so app can read its own location|
| `APP_SIZE` | r/w | r | 4B | u32 | | Firmware stores app app size here, so app can read its own size |
| `CDI_FIRST` | r/w | r | 32B | u8[32] | | Compound Device Identifier (CDI). UDS+measurement... |
| `CDI_LAST` | | r | | | | Last word of CDI |