The thirty-two 32-bit or 64-bit General Purpose Registers are numbered R0 through R31. The register file is reset on bit stream download (reset value is 0x00000000). The following figure is a representation of a General Purpose Register and the following table provides a description of each register and the register reset value (if existing).
When 64-bit MicroBlaze is enabled
(C_DATA_SIZE = 64), the General Purpose Registers have 64 bits,
otherwise they have 32 bits.
Note: The register file is not reset by the external reset inputs:
Reset and Debug_Rst.Figure 1. R0-R31
| Bits 1 | Name | Description | Reset Value |
|---|---|---|---|
|
R0 | Always has a value of zero. Anything written to R0 is discarded | 0x0 |
| R1 through R13 | General purpose registers | - | |
| R14 | Register used to store return addresses for interrupts. | - | |
| R15 | General purpose register. Recommended for storing return addresses for user vectors. | - | |
| R16 | Register used to store return addresses for breaks. | - | |
| R17 | If MicroBlaze is configured to support hardware exceptions, this register is loaded with the address of the instruction following the instruction causing the HW exception, except for exceptions in delay slots that use BTR instead (see (Branch Target Register)); if not, it is a general purpose register. | - | |
| R18 through R31 | General purpose registers. | - | |
|
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See (Table 1) for software conventions on general purpose register usage.