May 2, 2025

STM32H743 Nucleo board -- Cortex-M7 SCB registers

SCB is the system control block, with registers at base address 0xe000e000. There are other blocks of addresses in the 0xe0000000 area. These are actually part of the ARM core, not peripherals added by ST.

The are shown in the following link, which is Table 3-1 from the "ARM Cortex-M7 Processor Technical Reference Manual r1p1".

The first thing the demo code does is: 
0802b1f0:   4823        ldr r0, [pc, #140]   ;  0xe000ed88  (0x802b280)
0802b1f2:   6800        ldr r0, [r0, #0]
0802b1f4:   f450 0070   orrs.w  r0, r0, #0x00f0_0000
0802b1f8:   4921        ldr r1, [pc, #132]   ;  0xe000ed88  (0x802b280)
0802b1fa:   6008        str r0, [r1, #0]
This register (at offset 0xd88) is the "Coprocessor Access Control Register". Writing the 4 bits as shown gives full access to the FP extension.

Systick registers

This also is in this zone of addresses and has 4 registers: 
0xE000E010	SYST_CSR	RW	Privileged	0x00000004	SysTick Control and Status Register
0xE000E014	SYST_RVR	RW	Privileged	UNKNOWN	SysTick Reload Value Register
0xE000E018	SYST_CVR	RW	Privileged	UNKNOWN	SysTick Current Value Register
0xE000E01C	SYST_CALIB[b]	RO	Privileged 0xC0000000 SysTick Calibration Value Register
This is described in a different document, the "Arm Cortex-M7 Devices Generic User Guide r1p2" in table 4-33
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Tom's Computer Info / tom@mmto.org