Motorola ASTRO XTSTM 4000 Detailed Service Manual Download

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May 28, 2008

6871620L01-C

3-16

VOCON Section

3.2.2.1.2 Digital Signal Processor (DSP)

The DSP portion of the Patriot IC has 84k x 24 bits of program RAM and 62k x 16 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 section. The BBP has independent sections for the receiver and the transmitter. The
receiver BBP pins include the receive data pin SRDB (R1110), the receive clock signal pin SC0B
(R1109), and the receive frame synchronization (sync) signal pin SC1B (R1111). The transmitter's
BBP pins include the transmit data pin STDB (R1113), the transmit clock signal pin either SCKB
(R1112), and the transmit frame sync signal pin either SC2B (R1114). All BBP lines use GPIO
voltage logic levels.

DSP Timer Module

While the BBP receive clock and frame sync signals are supplied by the Abacus III IC from the
transceiver section, 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 T10, 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 section.

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 MAKO IC.

The SAP also interfaces with the encryption module.

The SAP interface consists of four signals including the SAP clock line pin SCKA (component
R1410), the SAP frame sync line pin SC2A (component R1411), the SAP receive data line pin SRDA
(component U1408), and the transmit data line pin STDA (component R1338).

The SAP clock is generated by the dual-core processor U1401, and is a 256 kHz, 2.9 V peak-to-
peak square wave. The SAP frame sync signal is generated by the dual-core processor U1401, and
is an 8 kHz, 2.9 V 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 MAKO IC
USB2_OE_RCV_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 MAKO IC
USB1_DAT_TXD pin. The USB transmit single-ended zero signal is generated from the Patriot IC
PC0_USB_VMOUT pin.