Sbep Serial Interface; General Purpose Input/Output; Normal Microprocessor Operation - Motorola GM950E Service Manual

The timing and operation of this interface is specific to the option connected, but generally follows
the pattern:
1) an option board device generates the interrupt,
2) main board asserts a chip select for that option board device,
3) the main board µP generates the CLK, and
4) when data transfer is complete the main board terminates the chip select and CLK activity.
2.9

SBEP Serial Interface

The SBEP serial interface allows the radio to communicate with the Radio Service Software (RSS).
This interface connects to the Microphone connector (J0903/J0803) via Control Head connector
(J0101) and comprises BUS+ (J0101-15). The line is bi-directional, meaning that either the radio or
the RSS can drive the line.
When the RSS needs to communicate with the radio, an interrupt is generated by the BUS+ signal
through R0104. The µP then starts serial data communication on BUS+ by sending data from pin 50
through D0101 and receiving data at pin 47 through R0104. While the radio is sending serial data at
pin 50 it receives an "echo" of the same data at pin 47.
2.10

General Purpose Input/Output

The Controller provides six general purpose lines (GP1 through GP6) available on the accessory
connector J0400 to interface to external options. Lines GP1,4 are inputs, GP2 is an output and
GP3,5,6 are bidirectional. The software and the hardware configuration of the radio model define the
function of each port. Some ports are not connected on the 4ch radio, refer to appendix B.
GP1 can be used as external PTT input or others, set by the RSS.
GP2 can be used as normal output (Q0441 placed) or external alarm output (Q0442 placed). The
voltage range can be set by R0442 (0-5V) or R0443 (0 - supply voltage).
GP4 can be used as normal input (D0471, R0477 not placed) or emergency input (D0471, R0477
placed).
GP3,5,6 are bidirectional and use the same circuit configuration. Each port uses an output transistor
controlled by µP port PB5,4,7 and an input transistor read by µP port PC2,5,3. To use one of the
GP´s as input the µP must turn off the corresponding output transistor.
In addition the signals from GP3-6 are fed to the option board connectors J0102, J0103.
The 470pF and 10nF capacitors serve to filter out any AC noise which may ride on the GP lines.
2.11

Normal Microprocessor Operation

The E9/20µP (U0101) contains internal 12 (E9) or 20 (E20) Kilobytes ROM, 512 (E9) or 768 (E20)
bytes SRAM and 512 bytes EEPROM.
The E9/20µP RAM is always powered to maintain parameters such as the last operating mode. This
is achieved by maintaining 5V at U0101-25. Under normal conditions, when the radio is off UNSW
+5V is formed by FLT A+ running to D0621.
Theory of Operation
Controller
6.3-5