CTI Products TSAM Transmitter Steering & Audio Matrix - Manual (Page 72)

TSAM Installation and Maintenance Rev. 2.10 Chapter 8
CTI Products, Inc. Maintenance Theory
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Each SPI transfer or command ends with the SPI command data. The last 8 bits of data shifted out on
MOSI MCU line are loaded in the command shift register. These 8 bits contain the TSAM board address
and command data.
Bit Number Signal Name Function
8 BC Reserved
7 A2 Board Addr MSB
6 A1 Board Addr Bit1
5 A0 Board Addr LSB
4 C3 Command word MSB
3 C2 Command word Bit2
2 C1 Command word Bit1
1 C0 Command word LSB
When the proper command value and address value are shifted out the SPI bus, the command decoder on
each TSAM determines if the address bits match the board address switch. When a match is detected, the
control function is enabled thereby setting or clearing the control line outputs of the command decoder.
The Output Shift Register (IC132) has 32 to outputs that can be set or cleared by the MCU. Many of these
outputs are used to control the TX and RX crosspoint switches. Even though the crosspoint switch arrays
(IC111 and IC205) are not directly connected to the SPI bus, the MCU programs them through the SPI via
the Output Shift Register.
RS-232 Serial Interface
The TSAM is a flexible unit that can be tailored to the needs of a particular installation. Parameters such
as the steering algorithm, and timing parameters are easily altered through the programming port. The
programming port uses an industry standard RS-232 interface.
The MCU's internal SCI communications port uses standard TTL voltage levels. IC123 converts these to
RS-232 levels. IC123 has two on chip charge pump voltage generators. They generate approximately
±
10V unloaded. This voltage drops to ±3V at full load. The charge pump voltages can be measured at
IC123 pins 2 and 6. Pin 7 of IC123 provides a DCD indication to satisfy handshaking requirements for
the programming terminal. This line should measure +3 to +10 Volts after the MCU is reset, it is always
asserted while the MCU is running.
The programming port connector J102 is wired as a 9 Pin PC AT DCE connector. This allows use of a
standard straight-through 9 Pin male to female cable. This is the most common portable/ laptop PC
connector.
A/D Converter
The MCU integrates an internal A/D converter. The converter is used for factory analog loop back tests.
Under MCU control the analog signal to be measured is routed through the crosspoint switch (IC111,
IC205). The signal appears on IC111 port X8. The signal is conditioned by IC114 and IC135. Three
conditioned signal are then connected to the MCU on the PE0, PE1, and PA0 lines. A peak detector
circuit conditions the signal on PE1. This provides a means for measuring the peak signal level of an
audio signal. A buffer conditions the PE0 signal that allows more complex measurements to be made of
the analog signal. A hard limiter (zero crossing detector) squares the analog signal applied to PA0.