Speb Serial Interface - Motorola GM-950 Manual

When the µP needs to program any of these IC's it brings the chip select line for that IC to a logic 0
and then sends the proper data and clock signals. The amount of data sent to the various IC's are
different, for example the FRAC-N can receive up to 21 bytes (168 bits) while the DAC can receive
up to 3 bytes (24 bits). After the data has been sent the chip select line is returned to a logic 1.
Version 0102726B09_Cntl and following versions: When the control head with graphical display
wants to communicate to the µP it brings request line ANALOG 2 (J0101-11) to a logic "0". The µP
reads this line via one of the analogue to digital converters (U0101-48) and then starts
communication by activating the control head select line (LED CHT CE) via U0105-9 and J0101-12,
sending the clock signal via U0106-3 and J0101-5 and sending data via U0106-2 and J0101-6 or
receiving data via J0101-10 and gate U0171. During data transfer gate U0171 is switched on by line
LED CHT CE via transistor Q0171 and gate U0172-1. Gate U0172-1 is enabled by the µP via ASFIC
output GCB4 (U0201-A2).
The Option board interfaces are different in that the µP can also read data back from devices
connected.The timing and operation of this interface is specific to the option connected, but
generally follows the pattern:
an option board device generates an interrupt via J0103-8, Q0124, Q0125 and µP pin 61
1.
(IRQ). The µP determines the interrupt source by reading a high at the collector of Q0124 via
µP pin 7 and R0129.
2. the main board asserts a chip select for that option board device via U0105-10, J0102-5,
the main board µP generates the CLK (J0102-6),
3.
the main board µP writes serial data via J0102-4 and reads serial data via J0102-2 and,
4.
5. when data transfer is complete the main board terminates the chip select and CLK activity.
2.10

SPEB Serial Interface

The SBEP serial interface allows the radio to communicate with the Radio Service Software (RSS)
via the Radio Interface Box (RIB). This interface connects to the Microphone connector (J0903/
J0803) via Control Head connector (J0101-15) or to the accessory connector J0400-6 and
comprises BUS+ (J0101-15). The line is bi-directional, meaning that either the radio or the RSS can
drive the line.
When the RIB (Radio Interface Box) is connected to the radio, a voltage on the HOOK RSS line
above 6 volts switches on Q0105. The low state at collector of Q0105 switches Q0104 off and in
turn, Q0106 on. A high to low transition at the collector of Q0106 generates an interrupt via µP pin
61. The µP determines the interrupt source by reading a high at the collector of Q0104 via µP pin 6
and R0125. The switched on Q0105 also switches off Q0122 enabling the µP to read BUS+ via pin
78 and to write BUS+ via pin 79 and transistors Q0123,Q0121. While the radio is sending serial data
at pin 79 via Q0123 and Q0121 it receives an "echo" of the same data at pin 78.
When the voltage on the HOOK RSS line is below 6 volts (RIB is not connected), the high collector
of Q0105 turns on Q0122. The low collector of Q0122 prevents the µP from writing data to BUS+ via
Q0123. In this mode line BUS+ is used for signal SCI RX of the Serial Communication Interface
(SCI). The µP reads the SCI via signal SCI RX (pin 78) and writes via signal SCI TX (pin 79). Both
signals are available on the accessory connector J0400 (SCI DATA OUT, SCI DATA IN).
Theory of Operation
Open Controller
5C.3-5