Nios® V Processor Reference Manual

ID 683632
Date 10/02/2023
Public

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3.4.2.1. Control and Status Register Field

The value in the each CSR registers determines the state of the Nios® V/m processor. The field descriptions are based on the RISC-V specification.

Table 39.  Machine Status Register FieldsThe mstatus register is a 32-bit read-write register that keeps track of and controls the hart’s current operating state.
Bit Field
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
SD WPRI TSR TW TVM MXR SUM MPRV XS[1:0]
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
XS[1:0] FS[1:0] MPP[1:0] WPRI SPP MPIE WPRI SPIE UPIE MIE WPRI SIE UIE
Table 40.  Machine ISA Register FieldsThe misa CSR is a read-write register reporting the ISA supported by the hart.
Bit Field
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
MXL[1:0] WLRL Extension[25:0]
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Extension[25:0]
Table 41.  Machine Interrupt-Enable Register FieldsThe mie register is a 32-bit read-write register that contains interrupt enable bits.
Bit Field
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
WPRI
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
WPRI MEIE WPRI SEIE UEIE MTIE WPRI STIE UTIE MSIE WPRI SSIE USIE
Table 42.  Machine Trap-Handler Base Address Register FieldsThe mtvec register is a 32-bit read/write register that holds trap vector configuration, consisting of a vector base address (BASE) and a vector mode (MODE).
Bit Field
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Base[31:2]
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Base[31:2] Mode
Table 43.  Machine Exception Program Counter Register FieldsThe mepc register is a 32-bit read-write register that holds the addresses of the instruction that was interrupted or that encountered the exception when a trap is taken into M-mode.
Bit Field
31 30 29 28 27 26 25 ... 6 5 4 3 2 1 0
mepc
Table 44.  Machine Trap Cause Register FieldsThe mcause register is a 32-bit read-write register that hold the code indicating the event that caused the trap when a trap is taken into M-mode.
Bit Field
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Interrupt Exception code [30:16]
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Exception code [15:0]
Table 45.  Machine Trap Value Register Fields The mtval register is a 32-bit read-write register that is written with exception-specific information to assist software in handling the trap when a trap is taken into M-mode.
Bit Field
31 30 29 28 27 26 25 ... 6 5 4 3 2 1 0
mtval
Table 46.  Machine Interrupt-Pending Register FieldsThe mip register is a 32-bit read/write register containing information on pending interrupts.
Bit Field
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
WPRI
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
WPRI MEIP WPRI SEIP UEIP MTIP WPRI STIP UTIP MSIP WPRI SSIP USIP
Table 47.  Trigger Select Register FieldsThe tselect register is a 32-bit read/write register that selects the current trigger is accessible by other trigger register.
Bit Field
31 30 29 28 27 26 25 ... 6 5 4 3 2 1 0
tselect
Table 48.  Trigger Data 1 (Match Control) Register FieldsThe tdata1 (mcontrol) register is a 32-bit read/write register containing information on the trigger type, tdata registers accessibility, and trigger implementation
Bit Field
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
type=2 dmode maskmax hit select timing sizelo
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
action chain match m 0 s u execute store load
Table 49.  Trigger Data 2 Register FieldsThe tdata2 register is a 32-bit read/write register containing the trigger-specific data.
Bit Field
31 30 29 28 27 26 25 6 5 4 3 2 1 0
tdata2
Table 50.  Trigger Info Register FieldsThe tinfo register is a 32-bit read-only register containing information on each possible tdata1.type.
Bit Field
31 30 29 18 17 16 15 14 13 2 1 0
0 info
Table 51.  Debug Control and Status Register FieldsThe dcsr CSR is a 32-bit read-write register containing information and status during D-mode
Bit Field
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
debugver 0
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
ebreakm 0 ebreaks ebreaku stepie stopcount stoptime cause 0 mprven nmip step prv
Table 52.  Debug Program Counter Register FieldsUpon entry to D-mode, dpc CSR is updated with the virtual address of the next instruction to be executed.
Bit Field
31 30 29 28 27 26 25 ... 6 5 4 3 2 1 0
dpc
Table 53.  Vendor ID Register FieldsThe mvendorid CSR is a 32-bit read-only register that provides the JEDEC manufacturer ID of the provider of the core.
Bit Field
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Bank
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Bank Offset
Table 54.  Architecture ID Register FieldsThe marchid CSR is a 32-bit read-only register encoding the base microarchitecture of the hart.
Bit Field
31 30 29 28 27 26 25 ... 6 5 4 3 2 1 0
Architecture ID
Table 55.  Implementation ID Register FieldsThe mimpid CSR provides a unique encoding of the version of the processor implementation.
Bit Field
31 30 29 28 27 26 25 ... 6 5 4 3 2 1 0
Implementation
Table 56.  Hardware Thread ID Register FieldsThe mhartid CSR is a 32-bit read-only register that contains the integer ID of the hardware thread running the code
Bit Field
31 30 29 28 27 26 25 ... 6 5 4 3 2 1 0
Hart ID