MA28140 Datasheet, PDF (3/72 Pages) Dynex Semiconductor – Packet Telecommand Decoder

TC input
NRZ or PSK
(6 max)
Transponder
I/F
Clock
External
Authentication
Unit
Local Bus
ROM
Configuration
Authentication
RAM
PTD
CPDU
I/F
MAP
Demultiplexer
I/F
MA28140
Back-up
Power
Supply
Command
Pulses
(256 max)
Serial
Data link
(62 max)
Telemetry
I/F
Figure 1: Block Diagram of a TC Decoder Subsystem
2. TC DECODER SUBSYSTEM OVERVIEW
An ESA/CCSDS Telecommand Decoder subsystem
including the PTD and fulfilling the receiving-end functions
established in the Packet Telecommand Standard (ref 1) is
shown in Figure 1.
The PTD requires the following additional hardware to fulfil
the requirements of the Telecommand Decoder Specification
(ref 2):
• Transponder I/F including demodulators for PSK TC
inputs.
• Telemetry I/F. The telemetry reporting signals can be
directly connected to a Virtual Channel Multiplexer (ref 3).
• Command Pulse Distribution Unit I/F. This function
performs decoding of commands present on the local bus
and power amplification. The PTD ASIC associated with
the CPDU I/F can manage 256 pulse outputs.
• MAP demultiplexer I/F. This interface is composed of a
demultiplexer to provide the TC segment data to various
Data Management System interfaces. The demultiplexer
is controlled by the MAP data present on the Local Bus.
The PTD ASIC can manage 62 different serial data
interfaces (63 if AU is disabled).
• Memories. There are 2 different memories:
- RAM (2Kx8) used to store the received TC data and
protocol variables (programme authentication key for
instance) and eventually to store the TC segment
available for further processing by the Data Management
System. If this memory is used to store the recovery LAC
counter (Authentication function), it must be a non-volatile
memory.
- ROM (1Kx8) divided in two parts:
- Configuration part, used to provide the Mission
Specific Data.
- Authentication part, used to provide the fixed
Authentication key.
• External Authentication Unit (optional). Although an AU is
implemented in the PTD, it is also possible to use an
external AU if the mission requires a different
authentication algorithm. This external unit accesses the
RAM in order to authenticate a TC segment.
3/72