SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
Some registers in the system are protected from spurious CPU writes by the EALLOW protection mechanism. This uses the special CPU instructions EALLOW and EDIS to enable and disable access to protected registers. The current protection state is given by the EALLOW bit in the CPU ST1 register, as shown in Table 3-1.
Register protection is enabled by default at startup. While protected, all writes to protected registers by the CPU are ignored. Only CPU reads, JTAG reads, and JTAG writes are allowed. If protection is disabled by executing the EALLOW instruction, the CPU is allowed to write freely to protected registers. After modifying registers, the registers can once again be protected by executing the EDIS instruction to clear the EALLOW bit.
Writes to the clock configuration and peripheral clock enable registers can be disabled until the next reset by writing to special lock registers.
EALLOW Bit | CPU Writes | CPU Reads | JTAG Writes | JTAG Reads |
---|---|---|---|---|
0 | Ignored | Allowed(1) | Allowed | Allowed |
1 | Allowed | Allowed | Allowed | Allowed |