Antelope Progress

• MMU and Cache->Datapath interfaces almost complete

• Datapath moving slowly, control issues keep surfacing

• Hazard Detection/Prevention coming along• IRQ/Exception handler is somewhat complete• Instruction Sequencer built, helps with multicycle

instructions and IRQ/Exception sequences

Main Memory

• Controlled by State Machine

• Successfully simulated with delays

• Left to do: Cache<-> Memory interface– State machine

Memory FSM

• Signals In:– Instruction read, Data read, Data write– Reset

• Signals out:– DataAddr, InstrAddr– select, r_w– valid, done

Memory Delay

• Gen_lib component: delay– Rise delay = 80 ns– Fall delay = 0 ns

• State Machine sets signal high and then waits for the signal to propagate through

• Loops in wait state

8 bit Cache Blocks(to enable byte transfer)

Cache <-> Memory

• Signals out:– Pipeline hold– LoadMem (cache write)

• Signals in:– Data write, Data read, Instruction read– Valid, Done– Dirty, hit

Instruction Sequencer

• Found that many multicycle instructions can be broken into a sequence of single cycle instructions.

• Wanted a way to trigger a sequence of instructions to run through the pipeline.

• Example: LDR/STR -> load the sequencer rom with an add/sub instruction and a custom ldr/str instruction. Activate the sequencer whenever LDR/STR runs through pipe.

Sequencer Logic

Sequencer Integration

• Sequencer is just placed in the fetch stage in parallel with the instruction cache.

• The sequencer determines whether or not it is in control of the datapath.

• If a sequence is requested, the PC is held at it’s current value (though I may have to decrement it…), and the sequencer inserts instructions into the datapath until it is done.

Datapath

Hazard Checking Logic

Checks to see if Rd (destination register) is read from in next 2

commands

Original Design

Overview

Block Data Transfer

Interrupt Handler

Component must handle the following seven cases:1. Reset (Highest Priority)

2. Data Abort

3. FIQ

4. IRQ

5. Prefetch Abort

6. Undefined Instruction

7. Software Interrupt (SWI) (Lowest Priority)

Implementation

• One ROM file handles memory addresses.

• 3-bit input leads to 32-bit address for PC.

• Second ROM file handles CPSR alterations.

• 4-bit input leads to lower 8 bits of CPSR.

• Priorities of the interrupts are handled with CLZ functionality.

• Lastly, no interrupts leads to “Active = 0”.

To do:

• Finish everything.