a2p/build/openroad/readme-dffram.md

A2P for OpenLane/Carousel

• manually replace inferred mem with array macros; eventually make all arrays components (inferred for FPGA, phys for tech)

• how do you integrate with OpenLane?

1. use built .v from dffram.py? and run a fixup after to place?
2. reference dffram.py module but don't include .v?
3. totally place/route dffram and then include it?
4. include/copy stuff from build dir to openlane somewhere?

Arrays to convert to DFFRAM

• IC (4K)

  reg [21:0] ways_0_tags [0:127];
  reg [31:0] ways_0_datas [0:1023];
  

  • tag: 128x22b
  • data: 1024x32b

• DC (4K)

  reg [21:0] DC_DIR_tags [0:127];
  reg [7:0] DC_DIR_data_symbol0 [0:1023];
  reg [7:0] DC_DIR_data_symbol1 [0:1023];
  reg [7:0] DC_DIR_data_symbol2 [0:1023];
  reg [7:0] DC_DIR_data_symbol3 [0:1023];
  

  • tag: 128x22b
  • data(4): 1024x8b

• GPR

  reg [31:0] RegFilePlugin_regFile [0:31] /* verilator public */ ;
  

  • 32x32b, 3 read, 1 write

Creating DFFRAM arrays

• REQUIRES DOCKER

• github.com/efabless/openlane/blob/master/README.md

# clone OpenLane
# make full-pdk

• github.com/Cloud-V/DFFRAM

# clone DFFRam
```export PDK_ROOT``` if not set up already
# optionally set design name for any builds; **doesn't set the output name**
# export FORCE_DESIGN_NAME=ram_32_32

GPR

• need 3r1w and DFFRam creates 2r1w reg; so need 2 regs, or 3 32x32 RAM, or custom 3r script

• -v 1R1W not supported; is this basically the same as ram_32_32??

• multiple arrays will be instantiated in single gpr module; use parameter to select gen style

RAM

#export FORCE_DESIGN_NAME=ram_32x32
dffram.py -s 32x32 -p $PDK_ROOT

REG

• building block :: corresponds to platforms///_building_blocks//model.v

#export FORCE_DESIGN_NAME=reg_32x32
dffram.py -s 32x32 -v 2R1W -p $PDK_ROOT -b sky130A:sky130_fd_sc_hd:rf

Tag Arrays, 4K

• need to make decellerator script to whack the extra 10 bits/word after place and then run rest of stuff

#export FORCE_DESIGN_NAME=ram_128x32
dffram.py -s 128x32 -p $PDK_ROOT

• OR try...

export FORCE_ACCEPT_SIZE=wtf
#export FORCE_DESIGN_NAME=ram_128x22
dffram.py -s 128x22 -p $PDK_ROOT
unset FORCE_ACCEPT_SIZE

Data Array, IC

#export FORCE_DESIGN_NAME=ram_1024x32
dffram.py -s 1024x32 -p $PDK_ROOT

Data Array, DC (4)

• DFFRam handles byte writes, so this is same as IC

#export FORCE_DESIGN_NAME=ram_1024x8
#dffram.py -s 1024x8 -p $PDK_ROOT

IC/DC arrays could be built using different subunits if better for layout/timing; 4KB = 128 lines x 32B.

Updating core manually

• this is compiling components on non-generated paths...

verilator --lint-only -Wno-fatal A2P_WB_RAM.v

• add gpr.v and module to top; can use this to test on FPGA with EXPAND_TYPE=`INFERRED