SPRUHM9H October 2014 – May 2024 TMS320F28075 , TMS320F28075-Q1 , TMS320F28076
Several control registers are protected from spurious CPU writes by the EALLOW protection mechanism. The EALLOW bit in status register 1 (ST1) indicates the state of protection as shown in Table 3-5.
EALLOW Bit | CPU Writes | CPU Reads | JTAG Writes | JTAG Reads |
---|---|---|---|---|
0 | Ignored | Allowed | Allowed(1) | Allowed |
1 | Allowed | Allowed | Allowed | Allowed |
At reset, the EALLOW bit is cleared, enabling EALLOW protection. While protected, all writes to protected registers by the CPU are ignored and only CPU reads, JTAG reads, and JTAG writes are allowed. If this bit is set, 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.