Motorola HT 1000 service manual Appendix a, Introduction Circuit Description

Appendix A

11

Secure Modules: NTN7279A, NTN7280A, NTN7281A, NTN7282A, and NTN7283A for MTS 2000 Radios

Introduction

Circuit Description

NOTE: The Secure Module is NOT serviceable. The information contained in this appendix is only meant to help determine whether a problem is due to the Secure Module or the radio itself.

The Secure Module is designed to digitally encrypt and decrypt voice data in Motorola’s MTS 2000 Series Handie-Talkie™ Portable Radios. The Secure Module uses a custom encryption integrated circuit (IC) and an encryption key variable to perform its encode/decode function. The encryption key variable is loaded into the Secure Module via the radio’s universal (side) connector from a hand held key variable loader. The encryption IC corresponds to the particular encryption algorithm purchased. The encryption algorithms and their corresponding kit numbers are:

•Data Encryption Standard (DES)NTN7279A

•DES-XLNTN7280A

•Digital Voice Protection (DVP)NTN7281A

•DVP-XLNTN7282A

•DVI-XLNTN7283A

The Secure Module, shown in Appendix Figure 1, operates from two power supplies. The first 5 volt supply (Vdd) is received from the controller board through connector plug P1 pin 2. This Vdd supply is turned on and off with the radio on/off switch. The second supply (UNSW B+) is received from the controller board through connector Plug P1 pin 1. UNSW B+ provides power to the Secure Module as long as the radio battery is in place.

Key variables are loaded into the Secure Module through connector P1 pins 13, 15, and 16. One key variable can be stored in the module at a time. The key variable is stored in volatile electronic memory, so it can only remain in memory as long as the radio is connected to a charged battery. If the battery is removed or if the battery fails, then a capacitor will allow the module to retain the key variable for at least 30 seconds while the battery is being replaced.

The radio’s host processor communicates with the Secure Module on the Serial Peripheral Interface (SPI) bus. The host processor is the master on this bus, while the Secure Module is a slave on the bus. The

Appendix A- 1