Encryption Module - Motorola ASTRO XTS 5000 Detailed Service Manual

4-28
The radio power-down sequence begins by opening the radio On/Off switch, which removes the
B+SENSE signal from the VOCON board. This does not immediately remove power because the
GCAP II IC has control of Q502 through Vref, and U301 through WDI maintains the GCAP II IC in an
active state. Both the MCU and Flipper IC monitor B+SENSE. After B+SENSE is removed, the
Flipper IC waits 125 ms. before releasing WDI to allow for software cleanup; however, the software
has the ability to prolong this time if it was necessary to complete its operations. When WDI is
released, the GCAP II IC shuts down its supplies and the rest of the radio through Q501.
4.4

Encryption Module

The encryption module operates from two power supplies (UNSW_B+ and SW_B+). The SW_B+ is
turned on and off by the radio's on/off switch. The UNSW_B+ provides power to the encryption
module as long as the radio battery is in place.
Key variables are loaded into the encryption module through connector J701, pin 1. Depending on
the type of encryption module, up to 16 keys can be stored in the module at a time. The key can be
infinite key retention or 30-seconds key retention, depending on how the codeplug is set up.
The radio' s host processor communicates with the encryption module on the Synchronous Serial
Interface (SSI) bus. The SSI bus consists of five signal lines. A communications failure between the
host processor and the secure module will be indicated as an ERROR 09/10 message on the
display.
To troubleshoot the encryption module, refer to the flowcharts in the chapter entitled
Charts.
April 15, 2002
Detailed Theory of Operation
: Encryption Module
Troubleshooting
68P81094C31-O