A MSP430
Microcontroller with
Custom Peripherals
Robust
Low
Power
VLSI
Alicia Klinefelter
Dept. of Electrical Engineering, University of Virginia
May 08, 2012
Context
[1]
 Wireless body sensor
nodes (BSN) often have
microcontroller for
processing
 Requires coding in custom ISA
or assembly on finished chip
 For flexible design
available to C-level
programmers, the
MSP430 is ideal
 Problem: Accelerators
not addressable!
[2]
2
Method
1. Explore MSP430 RTL (from OpenCores), become
familiar with peripherals template, and simulate
behavioral code in ModelSim a
2. Add new peripheral block (use existing RTL), verify in
ModelSim a
3. Learn UPF format and how to incorporate the file
within the synthesis flow a
4. Do a first-pass synthesis of the RTL not including UPF
to determine power numbers a
5. Complete simulations of original RTL to determine
functionality and power a
6. Complete synthesis of RTL using UPF and complete
simulations to determine functionality and power r
3
Architecture
[2]
 The most important file to edit is
openMSP430_defines.v for setup
information
 The peripheral address space is
assumed to be 512B.
 There are limitations to what
peripherals (that are provided)
can be used based on whether
you plan to synthesize this for an  Within the openMSP430 directory
taken from OpenCores, there is a
FPGA or as an ASIC.
"/trunk/core/sim" directory for
running behavioral simulations for
 Program and data memory are
all core instructions plus other test
separate (can both be RAMs)
features such as debugging,
clocking, and peripherals.


Run on Linux
Download Icarus Verilog and GTK Wave Viewer
4
Custom Peripheral


Designware divider: DW_div
Made extra peripheral addressable to MSP430

To do behavior simulations (in ModelSim, for example), you need to also include two files within
your Verilog work directory for this module to reference found in
$SYNOPSYS_ROOT/dw/sim_ver directory.


One ".v" file with the same name as your DesignWare component
One ".inc" file with the name of your component.
5
Getting Test Vectors: GTKWave
6
Getting Test Vectors: Modelsim AND
7
Getting Test Vectors: Modelsim XOR
8
Getting Test Vectors: Modelsim MULT
9
Getting Test Vectors: Modelsim DIV
10
Synthesis with DC: Setup

Within the MSP430 directories from OpenCores, there is a directory
including tcl scripts for DC synthesis:
openmsp430 --> trunk --> core --> Synopsys


Good foundation for commands in DC
The dw_foundations.sldb file needs to be accessible to the script. This file
can be found at the Synopsys root directory /<current version>/libraries/syn.
11
Synthesis with DC: Results
 DC and DFT completed for
MSP430 without errors.
 Assumed voltage of 1.2V and
frequency of 1MHz for fast
“dco_clk” and 32kHz for slow
“lfxt_clk”
 Used series of tcl scripts
compiled from examples in
class, example provided by
openMSP430 directory, and
commands from
documentation.
12
Synthesis with DC: UPF Design
 There is a GUI option for
creating UPF files from your
synthesized design called
visual UPF.
 Can select individual modules,
put them on separate power
designs, and add power
switches.
 This creates a UPF script to
use for the rest of the flow.
 Consideration: need to add
switch inputs on top-level
Verilog before implementing.
13
Formality: Pre-Layout
14
P&R with ICC: Power Grid
 Place and route was
completed in ICC and used a
set of scripts from the class
tutorial.
 The library setup was almost
identical (as in the class
tutorial). There is a script
titled "design_all.tcl" used as
template for most of design.
 Final command set was a
hybrid between what was
provided in the script and
using the GUI to manually do
things. The final script is
included in the /icc/scripts
directory.
15
P&R with ICC: Post-Route
 The standard cells were
than placed, the design
was routed, and filler
cells were added.
 To view the size of the
routed design, the ruler
was used to see that it
is ~350umx350um
 GDS and final netlist
exported
 Problems: Violated min
density % for metal
layers not used, but
ignored the DRC
warnings.
16
P&R with ICC: Visual Mode
 There is a visual mode
to view different
design qualities.
 Within the GUI, you
can go to View -->
Visual Mode to see
the options.
Cell Density
17
P&R with ICC: Visual Mode
 Peripherals and
execution unit took
up a lot of space!
Hierarchy
18
P&R with ICC: Visual Mode
Clock tree routing: LFXT
Clock tree routing: DCO
19
Formality: Post-Layout
20
HSPICE Simluations
 SPICE netlist found using Hercules command
 nettran -verilog openMSP430.v -cdl-a -cdl-s -sp-S verilog-b1 VDD -verilog-b0 VSS -rootCell openMSP430 sp ./saed90nm.cdl -outType spice -outName
openMSP430.sp
 Problem: SPICE format, not HSPICE
1. .SUBCKT <subckt name> <inputs and outputs> <BODY OF BLOCK>
.ENDS <subckt name>
2. Need an “.end” statement
 Created HSPICE stimuli file for ADD instruction
 v<NAME> <NAME> <GROUND REF> <TYPE OF SIGNAL> <VALUES>
 Needed to run for ~30μs (long!)
 Simulation took a few days
21
HSPICE Simluations Cont’d
 Include files in netlist:

.include "/net/plato.ee.virginia.edu/users/amk5vx/synopsys/msp430/hspice/_graphical_stimuli.scs"
.lib "/net/plato.ee.virginia.edu/users/amk5vx/synopsys/msp430/hspice/SAED90nm.lib" TT_12
 Add simulation type:

.TRAN 5e-9 34e-6 START=0.0
 Add node initial conditions:
 Had convergence problems, wrote Perl script to extract DFF nets

.IC
+ V(test_si2)=0
+ V(test_si3)=0
+ V(test_so3)=0
...
 Make simulation run faster:

.OPTIONS RELTOL=.01
.OPTIONS GMIN=10E-9
22
HSPICE Sim Results
 Viewed outputs using
Wave View (wv)
 AND simulation took a
few days (only one
instruction completed)
 The average current
was 30.8mA at 1.2V
and 1MHz. This results
in a power of 36.9mW.
23
Provided Results
 Directory of files including the results. The
description of each sub-directory is:
 dc: Results, scripts, ref files, and original Verilog files of the design for DC
synthesis.
 formality: Formality of pre and post layout files.
 hercules: Used for getting SPICE netlist from the results of ICC place and
route.
 hspice: directory containing HSPICE netlist, perl scripts for modifying SPICE
netlist to turn into an HSPICE netlist, and stimuli file.
 icc: Files and scripts used for place and route.
 Other loose files in the directory
 The data sheet for the DesignWare divider that is being used (dw_div.pdf)
 The "syn_setup" file that needs to be sourced before using all of the tools
described above.
24
Future Work
 Adding DesignWare or custom memories for
the program and data memories. The difficulty
isn't adding them so much as using them to
feed data to the MSP430 including all of the
scanning data into them and timing.
 More simulations of other instructions would
be good to truly know functionality across the
instruction set.
 Implementing power gating into the layout
using UPF.
25
References
1. Fan Zhang; Yanqing Zhang; Silver, J.; Shakhsheer, Y.; Nagaraju, M.; Klinefelter, A.;
Pandey, J.; Boley, J.; Carlson, E.; Shrivastava, A.; Otis, B.; Calhoun, B.; , "A batteryless
19μW MICS/ISM-band energy harvesting body area sensor node SoC," Solid-State
Circuits Conference Digest of Technical Papers (ISSCC), 2012 IEEE International , vol.,
no., pp.298-300, 19-23 Feb. 2012.
2. http://opencores.com/project,openmsp430
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Questions?
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