GSFC/NGIMS-FSW-05
CONTOUR/NGIMS COMMANDING
M Paulkovich
November 17, 1999
rev 1.00
PRELIMINARY


1  INTRODUCTION
This memo summarizes the approach for CONTOUR/NGIMS commanding, and will form the basis for the SIS-2 (level-2 Software Interface Specification).  This encompasses both Stored Commands and Telecommands.
STORED COMMANDS are contained in a sequence onboard the FC, triggered by S/C Time/Mode or by telecommand.  Stored Commands allow Scan Control and Mechanism Control (valves, dust trap, heaters, etc).
TELECOMMANDS are sent by GSE for Tuning Adjustments, Memory Loads (patches), Memory Dumps, Engineering Commands, and Stored Command Processor control (for testing).  All Stored Commands also have a Telecommand counterpart and thus, Telecommands also allow Scan Control and Mechanism Control.  Control over the Stored Command Processor software is also provided via Telecommands.  

Nomenclature
We must distinguish between "scanning sequences" and "stored command sequences" (among other things) in our nomenclature.  Definitions:  
IP - Integration Period (smallest unit in a scan); probably 15 or 20 ms for NGIMS. 
Subscan - A collection of around 10 to 20 IPs.  Note that telemetry is also grouped per Subscan.  
Scan Mode - One of the five round-robin modes: OS, CS, IM, PM, SS.
Scan - Complete traversal through one Scan Mode up to the commanded Last Subscan (qv). 
Pass - One traversal through five Scan Modes.  
Last Subscan - A commandable parameter
ATCS (Absolute Time Command Sequence) - The list of Stored Commands that run during a flyby.  
SCP (Stored Command Processor) - the software that runs the ATCS. 
Telecommand (TC) - Command from ground to the instrument. 
Script - A file on the GSE which contains both TCs and GSE commands (e.g., "wait" commands are GSE-only). 

The following flow diagram illustrates the relationship of stored commands and telecommands to scan control and other instrument operation. 




2  Stored Commanding 

The format the APL chooses for the T-zero (closest approach) message (currently unknown) may dictate whether ATCSs (Absolute Time-tagged Command Sequences) or RTCSs (Relative) are used for stored commands. We are baselining ATCSs.  ATCSs will be created and maintained by the CO-Is in an easily readable format (e.g. in a spreadsheet); a software tool will be used to convert the spreadsheet version of the ATCSs into machine format (binary/hex) for object file creation, PROM burning and/or telecommanding.  

An example of a section of a Stored Command Sequence is shown below. 


Command
Time
Comments
Valve 3, 1
0:10
Open valve 3
SetRepeat 1, 2, 0, 0
0:20
Set repeat count and scan parameters, Seq #1
OSBias 2
0:20
Set Open Source bias to 2
Valve 3, 0
0:30
Close valve 3
SetRepeat 1, 4, 0, 0
1:50
Set repeat count and scan parameters, Seq #1



    . . .
. . .
. . .




Example Stored Command Sequence



3  Command Dictionary
The following table delineates the current thinking on the list of Telecommands and Stored Commands.  

Command
Mnemonic
Parameters
SC
TC
Description
Adapt. Mass Tbl
MassTable
SS, Table
Y
Y
Select mass table Table for Subscan #SS for Scan Mode #4 (Programmed Masses)
Set Repeat Count
SetRepeat

Mode, 
RepeatCnt, 

Y
Y
For Scan Mode number Mode, set the subscan repeat count to RepeatCnt (0..63). 

Acquire Baseline
AcqBL
n/a
Y
Y
TBS (used in smart scanning)
Dust Trap Open/Close
DustTrap
Op (Open/Close) 
Y
Y
Open or close the rock collector
Test Mode
Test
Op (On/Off)
N
Y
"On" Enables subsequent test-only commands
Sequence Start
Start
n/a
N
Y
Start/resume the ATCS
Sequence Pause
Pause
n/a
N
Y
Pause the ATCS
Sequence Rewind
Rewind
n/a
N
Y
Rewind and stop the ATCS
Smartscan Control
TBD
TBD
Y
Y
TBD 
Scan Mode Control
Scan
Mode, Frac, LastSS
Y
Y
Allows Fractional (if Frac set) and partial scans (if LastSS nz) for Scan Mode Mode.
Filament (n) On/Off
Fil
Fil , 
Op (On/Off) 
Y
Y
On/Off control for each filament
Heater (n) On/Off
Htr
Htr,
Op (On/Off) 
Y
Y
On/Off control for each heater
Valve (n) Open/Close
Valve
Vlv, 
Op (Open/Close) 
Y
Y
Open/Close control for each valve
Temperature Control
Temp
Htr, 
OnPeriod, 
OffPeriod
Y
Y
Allow control of heater duty cycles
DAC Override Mode
DACORide
DAC, 
Op (On/Off) 
Y
Y
Causes DAC value for DAC #DAC  to freeze at current computer-generated state with subsequent control governed only by receipt of DAC teleommands (until DACORide Off) received). 
OS Bias
OSBias
Fil, 
Data
Y
Y
Set 2-bit bias value for fil # Fil on Open Source
BA On
BA
Op (On/Off) 
N
Y
Turn BA Filament On/Off
EM Select
EM
Sel (0 / 1)
Y
Y
Select EM 0 or 1
RAM Dump
RamDump
StartAddr, 
Length
N
Y
Request contents of RAM memory area
IORAM Dump
IORamDump
StartAddr, 
Length
N
Y
Request contents of IORAM memory area
CMP (Patch) Load 
Patch
StartAddr, 
Length, 
Data
N
Y
Load CMP (Computer Memory Patch)
EEPROM Init
EEPROMI
Bank
N
Y
Initialize (erase) all of EEPROM in Bank (1 or 2)
EEPROM Dump
EEPROMDump
StartAddr, 
Length
N
Y
Request contents of EEPROM memory area
Reboot
Reboot
n/a
N
Y
Boot from EEPROM (Test Mode Only)
TGO Boot
TgoBoot
n/a
N
Y
Cool reboot by TGO timer expiration and HW reset (Test Mode Only)
Force Experiment SW
ESW
Data1, 
Data2, 
Data3, 
Data4 
N
Y
Force value into ESW (Test Mode Only)
Sleep 
Sleep
n/a
Y
Y
Command the instrument to Standby (Sleep) mode
Raw I/O 
RawIO
Port, 
Data 
N
Y
Diagnostic capability to output to any 1750 I/O port (Test Mode Only)
No-Op
Noop
n/a
Y
Y
No operation
End Of List
EOL
n/a
Y
N
Signifies end of the Stored Command list
DAC Parameters
DACn
Data
Y
Y
Allow tuning of specified D/A. Only honored for specified DAC# (n) after DACORide On received for that DAC#. 





4  GSE Considerations

4.1  Remote Control.  It will be advantageous to include simple TCP/IP connections to the GSE for the sake of flexibility.  Moreover, this allows certain types of enhancements to be added by GSFC (by means of secondary GSE nodes) without requiring GSE software modification by SPRL.  
Thus it is suggested that a small feature be incorporated into the GSE to allow control via another node.  This can be as simple as designating a TCP/IP port that the GSE monitors for GSE commands.  This would allow great flexibility, in that another node (e.g. Lab software) could be used to control the Instrument in the GSE configuration.  

4.2  Remote Data Reduction.  It is also suggested that a small feature be incorporated into the GSE wherein all TM is echoed to a port (socket or IP) which is easily configurable via the GSE interface.  This will allow us to customize easily special software tools to display and filter TM during test and calibration.  


4.3  Special TM File/Display.  In Cassini, we assigned 8 bits to a "Serial Number" which was used to identify TCs.  For CONTOUR, 16 bits have been assigned.  We should consider using a couple of bits in the Serial Number as a flag to the GSE to route TM data to special displays.  For instance: 

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Destination
Serial Number

Assigning two bits to a GSE "Destination" allows the team to create TC scripts that direct selected TM packets to special GSE display windows.  This is possible because each TM packet echoes the most recent telecommand, including the Serial Number word.  
 

4.4  Voltage Scans.  With Cassini/INMS, voltage scans were performed by changing the DAC data on an IP-by-IP basis.  The current NGIMS scheme doesn't allow complete IP by IP control of DACs for special cases like voltage scans.  But via TC scripts, DACs can be scanned at an acceptable rate (less than one second per step).  This is done using the DAC Override and DAC commands.  

Using TC scripts along with the Destination bits proposed in 4.3 above, the important end result of voltage scans (commanded via the scripts) -- the TM --  can be displayed in special windows without being cluttered with data from "unimportant" IPs where the data was not changing. 


APPENDIX I
COMMAND FORMATS

1.  Command Argument Length Determination

Table 1 assigns OpCodes ("OC" column) and lists the required length of arguments for all commands, with a Total column for SCs only.  It is desirable to keep Stored Commands a constant length, and maintain the same header format for commands that are both TCs and SCs.    


Table 1 - Command Argument Lengths





Tot for SCs only

OC
Mnemonic
Parameters
SC
TC
Arg #bits
Tot
LSB & units
0
(spare)






1
MassTable
SS,
Table
Y
Y
SS - 5 bits
Table - 10 bits

15
SS - 1 n.u.
Table - 1 n.u.
(allows 1024 mass/config tables)
2
SetRepeat

Mode, RepeatCnt
Y
Y
Mode - 3 bits
RepeatCnt - 8 bits

11
Mode - 1 n.u. 
RepeatCnt - 0.25 n.u.; 0..63

3
AcqBL

Y
Y
n/a
0
n/a
4
DustTrap
Op (Open/Close )
Y
Y
Op - 1 bit
1
n/a (boolean)
5
Test
Op (On/Off)
N?
Y
Op  - 1 bit
1
n/a (boolean)
6
Start
constant: Op=1
N
Y
Op  - 2 bits
2
n/a 
6
Pause
constant: Op=2
N
Y
Op  - 2 bits
2
n/a
6
Rewind
constant: Op=3
N
Y
Op  - 2 bits
2
n/a
7
Smartscan
TBD
Y
Y
TBD

TBD
8
(spare)






9
(spare)






10
Scan
Mode, Frac, LastSS
Y
Y
Mode - 3 bits
Frac - 1 bit
LastSS - 2 bits
6
Mode - 0..5 n.u. 
Frac - n/a (boolean)
LastSS - 0 = 1-300, 
1 = 1-TBD, 2 = 1-TBD, 
3 = 1-TBD
12
Fil
Fil , On/Off 
Y
Y
Fil - 2 bits
On/Off  - 1 bit
3
n/a (boolean)
13
Htr
Htr, On/Off 
Y
Y
Htr - 2 bits
On/Off  - 1 bit
3
n/a (boolean)
14
Valve
Vlv, Open/Close
Y
Y
Vlv  - 3 bits?
Open/Close  - 1 bit
4
n/a (boolean)
15
Temp
Htr, OnPeriod, OffPeriod
Y
Y
Htr - 2  bits TBC
OnPeriod - 4 bits
OffPeriod - 4 bits
10
Htr - n.u.
OnPeriod - 0.5 (range 0..7.5) 
OffPeriod - 0.5 (range 0..7.5)
16
(spare)






17
DACORide
DAC, On/Off
N
Y
DAC - 5 bits
On/Off  - 1 bit

DAC - 1 n.u.
On/Off - n/a (boolean)
18
(spare)






19
OSBias
Fil, Data
Y
Y
Fil - 2 bits
Data  - 2 bits
4
Set 2-bit bias value for fil # Fil on Open Source
22
BA
Op (On/Off)
N
Y
On/Off - 1 bit

Turn BA Filament On/Off
23
EM
Em1
Y
Y
On/Off - 1 bit
1
Select EM 1 or 0
24
RamDump
StartAddr, Length
N
Y
Start Address - 16 bits
Length - 4 bits TBC 

Start Address - n.u.
Length - n.u.  Note issue on length: should be equal to or less than #IPs/Subscan
25
IORamDump
StartAddr, Length
N
Y
Start Address - 16 bits
Length - 4 bits TBC

Start Address - n.u.
Length - n.u.
26
Patch
StartAddr, Length, Data
N
Y
Start Address - 16 bits
Length - 4 bits TBC
Data - 16 bits each 
TBD: RAM | EEPROM

Start Address - n.u.
Length - n.u
Data - n.u. 
Note: Contour limit for TCs is 64 words incl. CCSDS hdr.
27
EEPROMI
Bank
N
Y
Bank - 1

Bank - n.u.
28
EEPROMDump
Bank, StartAddr, Length
N
Y
Bank - 1 
Start Address - 16 bits
Length - 4 bits TBC

Bank - n.u.
Start Address - n.u.
Length - n.u.
29
Reboot

N
Y
n/a

n/a
30
TgoBoot

N
Y
n/a

n/a
31
ESW
Data1, Data2, Data3, Data4 
N
Y
Data1..4: 16, 16, 16, 16

Data (n) - n.u.
32
Sleep

Y?
Y
n/a
0
n/a
33
RawIO
Port, Data 
N
Y
Port - 16 bits 
Data - 16  bits

Port - n.u.
Data - n.u.
34
Noop

Y
Y
n/a
0
n/a
35
EOL

Y
N
n/a
0
n/a
36
DACORide
DAC, On/Off
N
Y
DAC - 5 bits
On/Off  - 1 bit
6
DAC - 1 n.u.
On/Off - n/a (boolean)
37
DAC1
Data
Y
Y
Data  - 14 bits
14
14 bits max
38
DAC2
Data
Y
Y
Data  - 14 bits
14
14 bits max
39
DAC3
Data
Y
Y
Data  - 14 bits
14
14 bits max
40
DAC4
Data
Y
Y
Data  - 14 bits
14
14 bits max
37
DAC5
Data
Y
Y
Data  - 14 bits
14
14 bits max
38
DAC6
Data
Y
Y
Data  - 14 bits
14
14 bits max
39
DAC7
Data
Y
Y
Data  - 14 bits
14
14 bits max
40
DAC8
Data
Y
Y
Data  - 14 bits
14
14 bits max
41
DAC9






42
DAC10






43
DAC11






44
DAC12






45
DAC13






46
DAC14






47
DAC15






48
DAC16






49
DAC17






50
DAC18






51
DAC19






52
DAC20






53
DAC21






54
DAC22






55
DAC23






56
DAC24






57
DAC25






58
DAC26






59
DAC27






60
DAC28






61
DAC29






62
DAC30
spare?





63
(spare)









2.  Stored Commands - General Format

2.1  Common Fields.  The common fields for all commands (including TCs) will be:

OpCode
6 bits
Identifies the command
Checksum
6 bits
Used by FSW to validate command contents
VC
1 bit
"Validate Command" - see §3.2
FT
1 bit
"Fractional Time" - see §2.1.2
reserved
2 bits
reserved spares

  
2.1.1  Op Codes have been rather arbitrarily assigned in Table 1 above.  Six bits is adequate for an acceptable margin of spares for the OpCode field.  No consideration for hamming distance has been given since there is another error detection mechanism (checksum).  

From Table 1 we see the biggest argument for Stored Commands is ~15 bits.  Including the Header we can use constant length Stored Commands of two words.  This may change due to special Smart Scan issues as yet unknown.  

2.1.2  Stored Command Time Tags.  The Stored Command Time Tags must also be considered.  The longest time NGIMS is turned on for a comet encounter (Encke) is 14.6 Hrs.  A sixteen-bit word with 1s resolution covers 18.2 Hrs.  It may be desirable to allow 1/2 sec steps in Stored Commands; thus a reserved bit in the Header has been designated for Fractional Time (FT in the figure below).  

Figure 2-1  Stored Command Format
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
OpCode
Data Word
TimeTag
 VC =Validate Command 
 FT = Fractional Time (TimeTag LSB, =0.5s) (used only in SCs)
 

3.  Telecommands - General Format

3.1  Telecommands will use common fields as identified above in §2.1.  The differences between Stored Command and Telecommands are:
	TCs need no Time Tag
	TCs have variable length Data segments
	TCs have Serial Numbers (and ID which is reflected in TM, used to assist data analysis).

The general format for Telecommands will thus be: 

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
OpCode
Data Word 1

Data Words 2+
(number of words dependent upon OpCode & Data Word 1

SN
 VC =Validate Command 
 FT = Fractional Time (TimeTag LSB, =0.5s) (used only in SCs)


See also 5.3 regarding the SN for "Special TM File/Display."

3.2  There is a special case for "Non-Validated Commands" (Ground Test) - the VC bit (Validate Command).  When FSW validates command, command is valid if if S/C Mode = Ground, Checksum = 0 and VC = 0 (no checksum computation required).  Otherwise, VC must always be SET (Flight) and checksums are compared.  This feature allows manual creation of TCs with no software tool.  



4.  Itemized Command Formats

Example formats for some commands are proposed below.  For convenience of implementation and testing, it is possible to allocate some fields at byte boundaries, and also to expand them to more than the minimum bits.  
All command formats will eventually be defined in the SIS-2 (level-2 Software Interface Specification).  


MassTable - OpCode 1

As SC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
0
0
1
sp
SS
Table
TimeTag


As TC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
0
0
1
sp
SS
Table
SN


SetRepeat - OpCode 2

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
0
1
0
sp
Mode
RepeatCnt
TimeTag


As TC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
0
1
0
sp
Mode
RepeatCnt
SN


AcqBL - OpCode 3

As SC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
0
1
1
spare
TimeTag


As TC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
0
1
1
spare
SN



DustTrap - OpCode 4

As SC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
1
0
0

Open
TimeTag


As TC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
1
0
0

Open
SN



Test - OpCode 5

As SC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
1
0
1

On
TimeTag


As TC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
1
0
1

On
SN



Start - OpCode 6, Operation 1

As SC: (n/a)

As TC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
1
1
0
sp
0
1
SN



Pause - OpCode 6, Operation 2

As SC: (n/a)

As TC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
1
1
0
sp
1
0
SN



Rewind - OpCode 6, Operation 3

As SC: (n/a)

As TC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
0
1
1
0
sp
1
1
SN



Fil - OpCode 12 (14h)

As SC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
1
1
0
0
sp
Fil
sp
On
TimeTag


As TC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
1
1
0
0
sp
Fil
sp
On
SN



Htr - OpCode 13 (15h)

As SC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
1
1
0
1
sp
Htr
sp
On
TimeTag


As TC:

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
VC
FT
Checksum
sp
sp
0
0
1
1
0
1
sp
Htr
sp
On
SN



1