Motorola ASTRO XTS 5000 Detailed Service Manual page 50

4-14
One-Wire Interface
The MCU has a One-Wire Interface module that is used to communicate to a One-Wire device like a
USB cable or a smart battery using the Dallas Semiconductor protocol. This module has one
external pin, OWIRE_DAT (Q504 pin 2), and it uses a 3-volt logic level.
4.3.2.1.2 Digital Signal Processor (DSP)
The DSP portion of the Patriot IC has 84Kx24 bits of program RAM and 62Kx16 bits of data RAM.
The DSP has its own set of peripherals including the Baseband Interface Port (BBP), the DSP Timer
module, and the Serial Audio CODEC Port (SAP). Additionally, the DSP shares some peripherals
with the MCU, including the USB interface and the General Purpose Input/Output module (GPIO).
Baseband Interface Port (BBP)
The Baseband Interface Port (BBP) module is the DSP's serial synchronous interface (SSI) to the
transceiver board. The BBP has independent sections for the receiver and the transmitter. The
receiver BBP pins include the receive data pin SRDB (R121), the receive clock signal pin SC0B
(R124), and the receive frame synchronization (sync) signal pin SC1B (R123). The transmitter's BBP
pins include the transmit data pin STDB (R127), the transmit clock signal pin SCKB (R125), and the
transmit frame sync signal pin SC2B (R119). All BBP lines use 3-volt logic levels.
DSP Timer Module
While the BBP receive clock and frame sync signals are supplied by the Abacus III IC from the
transceiver board, the BBP transmit clock and frame sync signals are generated by the DSP Timer.
The BBP receive clock, connected to the DSP Timer input pin TI0, is reference used to generate the
BBP transmit clock and frame sync signals. These two signals, along with the BBP transmit data
signal, are connected to the DAC on the transceiver board.
Serial Audio CODEC Port (SAP)
The Serial Audio CODEC Port (SAP) module is the DSP's serial synchronous interface (SSI) to the
audio CODEC on the GCAP II IC. The SAP also interfaces with the encryption module.
The SAP interface consists of four signals including the SAP clock line pin SCKA (component R405),
the SAP frame sync line pin SC2A (component R406), the SAP receive data line pin SRDA
(component R402), and the transmit data line pin STDA (component R403). The SAP clock is
generated by the Flipper IC U301, and is a 520 kHz, 3-volt peak-to-peak square wave. The SAP
frame sync signal is also generated by the Flipper IC, and is an 8 kHz, 3-volt peak-to-peak square
wave.
Universal Serial Bus (USB)
The Patriot IC USB peripheral, shared by the MCU and the DSP, provides the required buffering and
protocol to communicate on the Universal Serial Bus. The Patriot IC supports USB slave
functionality.
For receive data, the USB differentially decoded data comes from the Flipper IC URXD_RTS pin into
the Patriot URTS1 pin, while the single-ended USB data positive signal goes to pin PA2_USB_VPIN,
and the single-ended USB data minus signal goes to pin URXD1. The two data lines are used to
detect the single-ended zero state.
For transmit data, the USB data comes out of the Patriot IC UTXD1 pin and goes to the Flipper IC
TXD_USB_VPO pin. The USB transmit single-ended zero signal is generated from the Patriot IC
PC0_USB_VMOUT pin.
April 15, 2002
Detailed Theory of Operation
: VOCON Board
68P81094C31-O