Florence Tan
FLIGHT CPU ELECTRONICS
Code 915/IDEA



OVERVIEW

* Block Diagram
* Design
CPU
Memory
Microsequencer interface
Spacecraft interface
* Tools/Other
* Differences between INMS and GCMS VS NGIMS designs
* Status


BLOCK DIAGRAM

DESIGN

CPU
MA31750 CPU running at 8 MHz
Includes watchdog timer which has to be refreshed every 0.65 seconds
Digital Electronics Heritage: INMS and GCMS
Combined 3 boards (PROM, CPU, BIU) from INMS to NGIMS CPU board.
NGIMS radiation environment 8Krads
All parts on INMS were qualified to a minimum of 100 Krads

Memory

Type
# Wds
Part #
Access t
Manu
Tot Dose
SEU LET
PROM
64K
SEI27C010TROE-10
100ns
SEI
>100Krads
>90MeV/mg/cm3
SRAM
64K
190A325-243
40ns
LMT
1Mrads
>120MeV/mg/cm3
EEPROM
128K
SEI28C010TRPFE-12
120ns
SEI
>100Krads
>90MeV/mg/cm3
IORAM
64K
190A325-243
40ns 
LMT
1Mrads
>120MeV/mg/cm3
Note:
No Wait states PROM and SRAM access
2 wait states IO access, EEPROM, IORAM
PROMs will be placed in a ZIF socket for easy software changes until two weeks before vibration and thermal vacuum testing. The ZIF will be removed and the flatpack PROMs will be installed before vibration and thermal vacuum testing. 

Spacecraft Interface

Mil-STD-1553B
Implemented using DC61582 hybrid with 16K words internal RAM and Mil-STD-21038/27-02 isolation transformers.
Transformer coupled (long stub) to 1553 bus

Microsequencer Interface

Completely defined because of INMS and GCMS heritage
Treated as IO ports and digital control ports

Tools/Other

A debug board with 12 7-segment LED, individual LEDs, and sound (to alert programmer of exceptions or interrupts)
RS232 download port for software uploads
Microsequencer simulator
HP 16500B logic analyzer with inverse assembler, pattern generator, and oscilloscope

Similarities and Differences (INMS & GCMS vs. NGIMS)

Similarities:

CPU
Watchdog circuitry
Configuration registers
Microsequencer interface
Interrupt handling
RAM and PROM addressing
IO paging

Differences:

Clock rate of CPU
Wait state generator circuitry - Number of waitstates per memory and IO device
IORAM and EEPROM addressing
Spacecraft interface (1553B)
Improved density parts (PROM, SRAM, EEPROM)
Debug board

Development Status

Board designed
Layout complete
Wirewrap board to be delivered 4/7/2000

Test and verification procedure

Use debug tools and microsequencer simulator
Reuse INMS test software

                    CONTOUR - Neutral Gas and Ion Mass Spectrometer
                                                                                                                                                         
Preliminary Design Review - March 31, 2000
Flight CPU Electronics



contour_pdr.doc						            GSFC/FT/ 1