Motorola ASTRO XTSTM 4000 Detailed Service Manual page 41

Theory of Operation: VOCON Section
Two main clocks are provided to the Patriot IC. The CKIH pin (C1402) is provided a 16.8 MHz sine
wave. This is the most important clock since it is internally used to generate the clocks for both the
MCU and DSP cores, as well as most of the peripherals. A 3 V peak-to-peak 32 kHz square wave
(32 kHz test point) is generated by the oscillator Y1301 and the buffer U1301, and supplied to the
CKIL pin on the Patriot IC. While not as widely used as the 16.8 MHz clock, the 32 kHz clock is
needed by some components in the Patriot including the reset circuitry.
3.2.2.1.1 Microcontroller Unit (MCU)
The MCU portion of the Patriot IC has 16k x 32 bits of internal RAM and 28k x 32 bits of internal
ROM, which is used for the bootstrapping code. The MCU has several peripherals including an
External Interface Module (EIM), the Multiple Queue Serial Peripheral Interface (MQSPI), two
Universal Asynchronous Receiver/Transmitter (UART) modules, and the One-Wire Interface
module. The MCU communicates internally to the DSP through the MCU/DSP Interface (MDI).
External Interface Module (EIM)
The External Interface Module (EIM) is the MCU interface to the SRAM U1409 and Flash Memory
U410, as well as the display module. The EIM lines include 24 external address lines, 16 external bi-
directional data lines, 6 chip selects lines, read/write line, and output enable line among others. All of
the EIM lines operate at 1.875-V logic levels, and the EIM operates at the MCU clock speed.
Multiple Queue Serial Peripheral Interface (MQSPI)
The Multiple Queue Serial Peripheral Interface (MQSPI) is the MCUs programming interface to other
ICs. The Patriot IC has two independent SPI busses, and each has its own clock line (test points
SCKA and SCKB), data-out line (test points MOSIA and MOSIB), and data-in line (test points MISOA
and MISOB). There are 10 SPI chip selects (SPICS) that are programmable to either SPI A, the
transceiver board SPI bus, or to SPI B, the dedicated VOCON SPI bus.
The devices on the SPI A bus include the PCIC and FracN IC on the SPICS4 (R1118), the Abacus III
IC on SPICS5 (R1119), and an analog-to-digital converter (ADC) on SPICS6 (R1120). One SPI B
chip select is used for the MAKO IC (U1304). All of the SPI module lines operate at GPIO voltage
logic levels.
Universal Asynchronous Receiver/Transmitter (UART)
The Patriot IC has two Universal Asynchronous Receiver/Transmitter (UART) modules. UART1
handles the RS232 lines while UART 2 is connected to the SB9600 lines. Each UART has a receive
data line (URXD), a transmit data line (UTXD), and hardware flow control signals (RTS–request to
send) and (CTS–clear to send). All UART lines operate at GPIO voltage logic levels. The translation
to 5 V logic levels for the accessory side connector is discussed in the MAKO section.
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 uses a GPIO
voltage logic level.
6871620L01-C
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May 28, 2008