Astro Spectra Plus Serial Peripheral Interface Bus; Astro Spectra Plus Mcu And Dsp System Clocks; Figure 3-18. Astro Spectra Plus Host Sb9600 And Rs232 Ports - Motorola ASTRO Digital Spectra Plus Service Manual

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The ASTRO Digital Spectra Plus radio has an additional asynchronous serial bus, which utilizes the
RS232 bus protocol. This bus utilizes the secondary UART in the Patriot IC (U300). It consists of TX
/ RS232 (J501-43), RX / RS232 (J501-50), CTS / RS232 (J501-5), and RTS / RS232 (J501-42). It is
a four-wire duplex bus used to connect to external data devices.

Figure 3-18. ASTRO Spectra Plus Host SB9600 and RS232 Ports

3.4.7

ASTRO Spectra Plus Serial Peripheral Interface Bus

This bus is a synchronous serial bus made up of a data, a clock, and an individual IC unique select
line. Its primary purpose is to configure the operating state of each IC. ICs programmed by this
include: ADDAG, Synthesizer, Prescaler, and the DAIC.
The MCU within the Patriot IC (U300) is configured as the master of the bus. It provides the
synchronous clock (SPI_SCK), a select line, and data (MOSI [Master Out Slave In]). In general the
appropriate select line is pulled low to enable the target IC and the data is clocked in. The SPI bus is
a duplex bus with the return data being clocked in on MISO (Master In Slave Out). The only place
this is used is when communicating with the ADDAG. In this case, the return data is clocked back to
the MCU on MISO (master in slave out).
3.4.8

ASTRO Spectra Plus MCU and DSP System Clocks

The MCU within the Patriot IC (U300) needs two clocks for proper operation. A 16.8 MHz sine-wave
reference is provided at the CKIH (A6) pin of the Patriot IC (U300). The source of this clock is a
16.8 MHz oscillator (Y400), and its associated filtering circuitry. This clock is also provided to the
KRSIC (U200), and the ADDAG IC (U201). The MCU has the capability of running at higher clock
rates, which are programmable and based on this 16.8 MHz reference. The DSP within the Patriot IC
(U300) also uses the 16.8 MHz provided at the CKIH (A6) pin as a reference.
The Patriot IC (U300) also requires a 32 kHz square-wave clock, provided at the CKIL (J7) pin. This
clock is generated by a 32 kHz crystal (Y401), with supporting circuitry for oscillation. This clock is
utilized only for the Patriot IC (U300), and is used for reset capability and other Patriot IC (U300)
functions.
October 28, 2002
Busy_RTS J501-20
LH / TX_Data J501-18
LH / RX_Data J501-17
TX / RS232 J501-43
RX / RS232 J501-50
CTS / RS232J501-5
RTS / RS232 J501-42
Theory of Operation: ASTRO Spectra Plus VOCON Board
PATRIOT
U300
URTS1
Primary
UTXD1
UART
URXD1
UTXD2
URXD2 Secondary
UART
UCTS2
URTS2
6881076C25-D