CUTE-I C&DH

Introduction

CUTE-I Command & Data Handling Subsystem (C&DH Subsystem) has two main functions. One is the function of receiving and executing commands from a ground station, the other is the function of gathering housekeeping data (HK data) and mission data of CUTE-I. To achieve these functions C&DH Subsystem consists of MPU (Micro Processing Unit), SRAM and so on.

System Block

The figure indicates the C&DH system block diagram. C&DH Subsystem consists of MPU, Memory, reset circuit and AD converter. The MPU is an 8bitMPU which has 32kbyte ROM and 1kbyte RAM. C&DH Subsystem has two types of memory; these are SRAM (4Mbit), which stores various sensor data, and EEPROM (256kbit), which stores status data for the initial sequence of C&DH Subsystem start-up. Though SRAM enables fast data access, it can’t keep data in the condition of power-off. Therefore C&DH has a small battery for data-back-up of SRAM. The reset circuit is used to reset MPU forcefully. The circuit can decode reset-command from a ground station and reset MPU. The AD converter (ADC) converts analog data to digital data. The MPU has some ADC, but an external ADC circuit is added because CUTE-I has many sensor devices that output analog data. C&DH Subsystem has 24 channels ADC in total.

CUTE-I C&DH Subsystem Block Diagram

About I/F

C&DH Subsystem has various I/F to CUTE-I subsystems, and I/F to ADS subsystem and communication subsystem is very important.

I/F of ADS Subsystem

Input from ADS Subsystem：	Attitude sensor data, etc.
Output to ADS Subsystem：	Switching command of multiplexer
Output to ADS Subsystem：	Control command for CMOS sun sensor

Input data from ADS Subsystem are Attitude, Temperature, Voltage and Current sensor data. These data are switched in multiplexers in ADS Subsystem by commands from C&DH Subsystem. C&DH Subsystem outputs an ON/OFF command and a luminance control signal which is used in the image processing to the Sun sensor of ADS Subsystem.

I/F of Comm. Subsystem

Input from Comm. Subsystem：	Reset signal for C&DH Subsystem
Output to Comm. Subsystem：	Packet data
	CW data
	Reset signal for Comm. Subsystem

Output data to Comm. Subsystem are packet data and CW data. Comm. Subsystem processes these data and transmits them to ground stations. C&DH and Comm. Subsystems watch each other at regular intervals. When one of them detects faults of the other, it sends a reset command.

C&DH Subsystem Circuit

front

We can see SRAM, EEPROM, reset circuit and so on. The small battery for data-back-up is placed over the SRAM. The black connecter at the lower part of the circuit is I/F to other subsystems. Through this connecter, C&DH Subsystem sends and receives data.

back

MPU is placed under the silver cover. There is a thermistor for measuring temperature between MPU and the silver cover.