SPI Test Status register. For functional testing only.
| RESERVED | Reserved, user software should not write ones to reserved bits. The value read from a reserved bit is not defined. |
| ABRT | Slave abort. |
| MODF | Mode fault. |
| ROVR | Read overrun. |
| WCOL | Write collision. |
| SPIF | SPI transfer complete flag. |
| RESERVED | Reserved, user software should not write ones to reserved bits. The value read from a reserved bit is not defined. |