Figure 3-49. Xtl 5000 Rx Signal Path - Motorola ASTRO Digital XTL 5000 Detailed Service Manual

Theory of Operation: Controller Section
Patriot
U100
SCKA
SRDA
SCKA
512kHz
TX Data
8kHz
The ABACUS III data is transferred to the Patriot IC at a 1.2 MHz bit rate, which is a synchronous
clock provided by the ABACUS III IC. The 20 kHz interrupt clock, also provided by the ABACUS III
IC, signals the arrival of a data packet and represents the sampling rate of the received data.
The DSP then processes this data to extract audio and signaling, perform filtering, alert-tone
generation, etc. The DSP performs de-emphasis and discrimination before sending the discriminator
data to the audio CODEC (U0200) via the SAP SSI bus. This bus is the digital audio bus consisting
of the 512 kHz master bit clock (SAP_DCLK), and the 8 kHz frame sync (SAP_FSYNC). These
clocks represent the data bit rate and sampling rate, respectively, for both the transmit and receive
digital audio. For secure messages, the digital signal data must be passed to the secure module for
decryption prior to DSP processing of the speaker data. The DSP transfers the data to and from the
secure module through the SAP SSI port TXD and RXD signals. Configuration and mode control of
the secure module is performed by the MCU through this bus.
The CODEC D/A analog output signal is routed to the RX_FILT_AUDIO line at both J0401 and
J0402/J2 for legacy accessories and special applications products at an amplitude of 100 mV per
kHz of deviation. The signal amplitude is independent of volume setting. This output is also routed to
a multiplex switch, U0210, which is one source of audio to the audio PA speaker output. The
alternate PA source, AUX_RX, is an input from J0401 and is used with vehicular repeater systems
(VRS). The multiplexer output, normally received speaker audio, is routed to a volume control digital
programmable potentiometer, U0206, and then to the audio PA (U0204) input. The audio PA output
then drives the external speaker.
6881096C74-B
SPI
S PI_SC
SPI_MOSI
SPI_MISO
SC0B
SAP BBP
SRDB
SC1B
CODEC
U0200
MCLK
DT
RO NEG
FSR

Figure 3-49. XTL 5000 RX Signal Path

PC
PD
ABACUS III
U6000
1.2MHz
ABA_CLK
RX Data
ABA_RXD
20kHz
ABA_FSYNC
Volume Pot
U0206
3-73
RF IN
SPKR+
Audio PA
(J0401-4)
U0204
SPKR -
(J0401-4)
MAEPF-27891-O
May 25, 2005