R32V2020 Register File

Register File Details

• 16 registers (r0-r15)
• All registers are 32-bits
• Some registers are dedicated and some registers are general purpose
• Almost all registers reset to zero at reset/power up

General Purpose Registers

• There are eight registers

Specialized Registers

• r0 - Always reads 0x0000
• r1 - Always reads 0x0001
• r2 - Always reads 0xffff
• r3 - Condition Code Register
• r4 - Stack Space Address Pointer
• r5 - Peripheral Space Address Pointer
• r6 - Data Space Address Pointer
• r7 - Instruction Space Address Pointer

r0 - Zero Value Register

• Read-only
• 0x0000 = value
• Set to 0x0000 at power up and reset

r1 - One Value Register

• Read-only
• 0x0001 = value
• Set to 0x0001 at power up and reset
• Useful for comparisons and two's complement math

r2 - All F's Register

• Read-only
• 0xFFFF = value
• Set to 0xFFFF at power up and reset
• Useful for two's complement math

r3 - Condition Code Register

• Bit field that represents the result of an ALU operation
  • d0 (LSB) = Result of operation was Equal to Zero
    • Used by BEZ opcode
  • d1 = Result of operation was Equal to One
    • Used by BE1 opcode
  • d2 - Carry Set (ex: adds can overflow into the carry bit) (
    • Used by BCS and BCC opcodes
  • d3 = Reached End of Stack Memory
    • Program exception
  • d4 = Reached End of Instruction Memory
    • Program exception
  • d5 = Reached End of Program Memory
    • Program exception
  • d6-d31 = Future Expansion

r4 - Stack Space Address Pointer

• Readable from CPU
• Written at push/pulls
• Stack Operational Details

r5 - Peripheral Space Address Pointer

• Read/Write from CPU
• Reset to 0x0000 at power up and reset

r6 - Data Space Address Pointer

• Read/Write from CPU
• Reset to 0x0000 at power up and reset
• Directly accesses BlockRAM attached to Data Address space address bits

r7 - Instruction Space Address Pointer

• Read/Write from CPU
• Reset to 0x0000 at power up and reset
• Auto-increment after Instruction is read
• Directly accesses BlockRAM attached to Instruction Address space address bits

Resources - Registers/Counters

• Total logic elements 594 / ~6000 ( ~10 % )
• Total registers 416
• Total memory bits 0 / 2,810,880 ( 0 % )
• Embedded Multiplier 9-bit elements 0 / 400 ( 0 % )
• Total PLLs 0 / 4 ( 0 % )

Resources - MUX_16x32

• Total logic elements 321 / 6,272 ( 5 % )
• Total registers 416
• Total memory bits 0 / 2,810,880 ( 0 % )
• Embedded Multiplier 9-bit elements 0 / 400 ( 0 % )
• Total PLLs 0 / 4 ( 0 % )