1 / 16

Register-Transfer Level (RTL) Design

Register-Transfer Level (RTL) Design. Recall Chapter 2: Combinational Logic Design First step: Capture behavior (using equation or truth table) Remaining steps: Convert to circuit Chapter 3: Sequential Logic Design First step: Capture behavior (using FSM) Remaining steps: Convert to circuit

lester
Download Presentation

Register-Transfer Level (RTL) Design

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Register-Transfer Level (RTL) Design • Recall • Chapter 2: Combinational Logic Design • First step: Capture behavior (using equation or truth table) • Remaining steps: Convert to circuit • Chapter 3: Sequential Logic Design • First step: Capture behavior (using FSM) • Remaining steps: Convert to circuit • RTL Design (the method for creating custom processors) • First step: Capture behavior (using high-level state machine, to be introduced) • Remaining steps: Convert to circuit Capture behavior Convert to circuit

  2. RTL Design Method

  3. T (in seconds) laser D Object of interest sensor 2D = T sec * 3*108 m/sec Step 1: Laser-Based Distance Measurer • Example of how to create a high-level state machine to describe desired processor behavior • Laser-based distance measurement – pulse laser, measure time T to sense reflection • Laser light travels at speed of light, 3*108 m/sec • Distance is thus D = T sec * 3*108 m/sec / 2

  4. B L from button to laser Laser-based distance 16 D S measurer to display from sensor Step 1: Laser-Based Distance Measurer • Inputs/outputs • B: bit input, from button to begin measurement • L: bit output, activates laser • S: bit input, senses laser reflection • D: 16-bit output, displays computed distance T (in seconds) laser sensor

  5. B L from button to laser Laser- based distance 16 D S measurer to display from sensor S0 ? L = 0 (laser off) D = 0 (distance = 0) Step 1: Laser-Based Distance Measurer • Step 1: Create high-level state machine • Begin by declaring inputs and outputs • Create initial state, name it S0 • Initialize laser to off (L=0) • Initialize displayed distance to 0 (D=0) Inputs: B , S (1 bit each) Outputs: L (bit), D (16 bits) a

  6. B L from button to laser Laser- based distance B’ (button not pressed) 16 D S measurer to display from sensor ? S1 B (button pressed) Step 1: Laser-Based Distance Measurer Inputs: B, S (1 bit each) • Add another state, call S1, that waits for a button press • B’ – stay in S1, keep waiting • B – go to a new state S2 Outputs: L (bit), D (16 bits) a S0 S0 L = 0 D = 0 Q: What should S2 do? A: Turn on the laser a

  7. B L from button to laser Laser- based distance 16 D S measurer to display from sensor S3 L = 0 (laser off) Step 1: Laser-Based Distance Measurer Inputs: B, S (1 bit each) • Add a state S2 that turns on the laser (L=1) • Then turn off laser (L=0) in a state S3 Outputs: L (bit), D (16 bits) B’ S0 S1 S2 B a L = 0 L = 1 D = 0 (laser on) Q: What do next? A: Start timer, wait to sense reflection a

  8. B L f r om but t on S’ (no reflection) t o laser Lase r -based distan c e 16 D S measu r er S (reflection) t o displ a y f r om sensor ? Dctr = 0 (reset cycle Dctr = Dctr + 1 count) (count cycles) Step 1: Laser-Based Distance Measurer Inputs: B, S (1 bit each) Outputs: L (bit), D (16 bits) • Stay in S3 until sense reflection (S) • To measure time, count cycles for which we are in S3 • To count, declare local register Dctr • Increment Dctr each cycle in S3 • Initialize Dctr to 0 in S1. S2 would have been O.K. too Local Registers: Dctr (16 bits) B’ S0 S1 S2 S3 B L = 0 L = 1 L = 0 a D = 0

  9. B L f r om but t on t o laser Lase r -based distan c e 16 D S measu r er t o displ a y f r om sensor S4 D = Dctr / 2 (calculate D) Step 1: Laser-Based Distance Measurer • Once reflection detected (S), go to new state S4 • Calculate distance • Assuming clock frequency is 3x108, Dctr holds number of meters, so D=Dctr/2 • After S4, go back to S1 to wait for button again Inputs: B, S (1 bit each) Outputs: L (bit), D (16 bits) Local Registers: Dctr (16 bits) S’ B’ a S0 S1 S2 S3 B S L = 0 Dctr = 0 L = 1 L=0 D = 0 Dctr = Dctr + 1

  10. Step 2: Create a Datapath • Datapath must • Implement data storage • Implement data computations • Look at high-level state machine, do three substeps • (a) Make data inputs/outputs be datapath inputs/outputs • (b) Instantiate declared registers into the datapath (also instantiate a register for each data output) • (c) Examine every state and transition, and instantiate datapath components and connections to implement any data computations Instantiate: to introduce a new component into a design.

  11. Local Registers: Dctr (16 bits) ‘ ‘ B S S4 S0 S1 S2 S3 B S L = 0 Dctr = 0 L = 1 L=0 D = Dctr / 2 D = 0 Dctr = Dctr + 1 (calculate D) D r eg_clr D r eg_ld clear clear I D c tr_clr D c t r : 16-bit D r eg: 16-bit c ou n t D c tr_c n t load u p - c ou n t er r e g is t er Q Q 16 D Step 2: Laser-Based Distance Measurer (a) Make data inputs/outputs be datapath inputs/outputs (b) Instantiate declared registers into the datapath (also instantiate a register for each data output) (c) Examine every state and transition, and instantiate datapath components and connections to implement any data computations Inputs: B, S (1 bit each) Outputs: L (bit), D (16 bits) a D a tap a th

  12. Local Registers: Dctr (16 bits) ‘ ‘ B S S4 S0 S1 S2 S3 B S L = 0 Dctr = 0 L = 1 L=0 D = Dctr / 2 D = 0 Dctr = Dctr + 1 (calculate D) >>1 16 16 Step 2: Laser-Based Distance Measurer (c) (continued) Examine every state and transition, and instantiate datapath components and connections to implement any data computations Inputs: B, S (1 bit each) Outputs: L (bit), D (16 bits) a D a tap a th D r eg_clr D r eg_ld clear clear I D c tr_clr D c t r : 16-bit D r eg: 16-bit c ou n t D c tr_c n t load u p - c ou n t er r e g is t er Q Q 16 D

  13. L B to laser from button Controller from sensor S Dreg_clr Dreg_ld Dctr_clr Datapath Dctr_cnt D to display >>1 16 300 M H z Clock 16 Datapath Dreg_clr Dreg_ld 16 Dctr_clr clear clear I Dctr: 16-bit Dreg: 16-bit Dctr_cnt count load up-counter register Q Q 16 D Step 3: Connecting the Datapath to a Controller • Laser-based distance measurer example • Easy – just connect all control signals between controller and datapath

  14. Inputs: B, S (1 bit each) Outputs: L (bit), D (16 bits) L B Local Registers: Dctr (16 bits) t o laser f r om but t on C o n t r oller r om sensor f S D r eg_clr B’ S’ D r eg_ld D c tr_clr D a tap a th S0 S1 S2 S3 S4 B S D c tr_c n t L = 0 Dctr = 0 L = 1 L=0 D = Dctr / 2 D D = 0 Dctr = Dctr + 1 (calculate D) t o displ a y 16 300 M H z Clock Inputs: B, S Outputs: L, Dreg_clr, Dreg_ld, Dctr_clr, Dctr_cnt B’ S’ B S S0 S1 S2 S3 S4 L = 0 L = 0 L = 1 L = 0 L = 0 Step 4: Deriving the Controller’s FSM • FSM has same structure as high-level state machine • Inputs/outputs all bits now • Replace data operations by bit operations using datapath a Dreg_clr = 1 Dreg_ld = 0 Dctr_clr = 0 Dctr_cnt = 0 (laser off) (clear D reg) Dreg_clr = 0 Dreg_ld = 0 Dctr_clr = 1 Dctr_cnt = 0 (clear count) Dreg_clr = 0 Dreg_ld = 0 Dctr_clr = 0 Dctr_cnt = 0 (laser on) Dreg_clr = 0 Dreg_ld = 0 Dctr_clr = 0 Dctr_cnt = 1 (laser off) (count up) Dreg_clr = 0 Dreg_ld = 1 Dctr_clr = 0 Dctr_cnt = 0 (load D reg with Dctr/2) (stop counting)

  15. Inputs: B, S Outputs: L, Dreg_clr, Dreg_ld, Dctr_clr, Dctr_cnt B’ S’ B’ S’ B S S0 S1 S2 S3 S4 B S S0 S1 S2 S3 S4 L = 0 L = 0 L = 1 L = 0 L = 0 Dreg_clr = 1 Dreg_ld = 0 Dctr_clr = 0 Dctr_cnt = 0 (laser off) (clear D reg) Dreg_clr = 0 Dreg_ld = 0 Dctr_clr = 1 Dctr_cnt = 0 (clear count) Dreg_clr = 0 Dreg_ld = 0 Dctr_clr = 0 Dctr_cnt = 0 (laser on) Dreg_clr = 0 Dreg_ld = 0 Dctr_clr = 0 Dctr_cnt = 1 (laser off) (count up) Dreg_clr = 0 Dreg_ld = 1 Dctr_clr = 0 Dctr_cnt = 0 (load D reg with Dctr/2) (stop counting) L = 0 Dctr_clr = 1 (clear count) L = 1 L = 0 Dreg_ld = 1 Dctr_cnt = 0 (load D reg with Dctr/2) (stop counting) Dreg_clr = 1 (laser off) (clear D reg) (laser on) Dctr_cnt = 1 (laser off) (count up) Step 4: Deriving the Controller’s FSM • Using shorthand of outputs not assigned implicitly assigned 0 a

  16. Datapath L B to laser from button from sensor S Dreg_clr Controller Dreg_clr Dreg_ld Datapath Dctr_clr clear clear I Dctr: 16-bit Dreg: 16-bit Dctr_cnt count load up-counter D register to display Q Q 300 MHz Clock 16 16 D Inputs: B, S Outputs: L, Dreg_clr, Dreg_ld, Dctr_clr, Dctr_cnt >>1 16 B’ S’ B S S0 S1 S2 S3 S4 16 L = 0 Dctr_clr = 1 (clear count) L = 1 L = 0 Dreg_ld = 1 Dctr_cnt = 0 (load D reg with Dctr/2) (stop counting) Dreg_clr = 1 (laser off) (clear D reg) (laser on) Dctr_cnt = 1 (laser off) (count up) Step 4 • Implement FSM as state register and logic (Ch3) to complete the design Dreg_ld Dctr_clr Dctr_cnt

More Related