Hello
If you want to do nothing on MCU, no-operation is used generally.
Additional mnemonics are provided for the preferred forms of no-op, like nop, e_nop, se_nop. (Where the semantics are similar but the binary encoding differ, the standard mnemonic is typically preceded with an e_ to denote a VLE instruction. To distinguish between similar instructions available in both 16- and 32-bit forms under VLE and standard instructions, VLE instructions encoded with 16 bits have an se_ prefix.)
When you compile these code within IDE, you can get the results as below.
The code could run correctly except __asm__ ("nop"). Some MPC5xxx will stop at __asm__ ("nop").
"nop" gives Book E NOP instruction which isn't valid on VLE only cores.
"e_nop" gives 32bit VLE instruction.
"se_nop" gives 16bit VLE instruction.
Based on the summary within AN4802 (thanks for Randy Dee's working), Qorivva MPC57xx e200zx Core Differences, Book E is not supported by MPC57xx. VLE instruction set is supported only.
This is the reason that user should use "e_nop" or "se_nop" except "nop" on MPC57xx or S32R2xx.
Cheers!
Oliver
