Sbep Serial Interface; General Purpose Lnpuuoutput - Motorola CDM1550 LS+ Detailed Service Manual

2-6 Theory of Operation
The option board interfaces are different in that the 1-1P can also read data back from devices
connected.The timing and operation of this interface is specific to the option connected, but the
general pattern is as follows:
Option board generates a service request via J0551, pin 29, line ROY, and IJP, pin 79
The main board asserts a chip select for that option board via U0141 ,pin 14, line OPT CS,
J0551 ,pin 30
The main board 1-1P generates the CLK (J0551 , pin 3)
The main board 1-1P writes serial data via J0551 , pin 15 and reads serial data via J0551, pin 16
When data transfer is complete the main board terminates the chip select and CLK activity
2.2.8 SBEP Serial Interface
The SBEP serial interface allows the radio to communicate with the Customer Programming
Software (CPS), or the universal tuner via the Radio Interface Box (RIB) . This interface connects to
the microphone connector via control head connector (J0401, pin 8) or to the accessory connector
J0401, pin 17 and comprises BUS+. The line is bi-directional, meaning that either the radio or the
RIB can drive the line. The 1-1P sends serial data via pin 98 and 00101 and it reads serial data via pin
97. Whenever the 1- 1 P detects activity on the BUS+ line, it starts communication.
In addition, the SBEP serial interface is used to communicate with a connected control head. When
a control head key is pressed or the volume knob is rotated, the line ON OFF CONTROL goes high .
This turns on transistor 00110 which pulls line ON OFF SENSE and 1-JP, pin 6 to ground level. In
addition, an interrupt is generated via R01 09 (for SELECT 5
I
MDC models) and IJP, pin 96. This
indicates that the control head wants to start SBEP communication. The 1-1P then reads the registers
of the Universal Asynchronous Receiver Transmitter (UART) U0125 to determine that the interrupt
source was the control head. If the interrupt source was from the control head , the 1-1P requests the
data from the control head. The control head starts sending and after all data has been sent, the ON
OFF CONTROL line goes low. The control head ignores any data on BUS+ during SBEP
communication with the CPS or universal tuner.
2.2.9 General Purpose Input/Output
The controller provides eight general purpose lines (DIG1 through DIGS) available on the accessory
connector J0501 to interface the external options. Lines DIG IN 1 ,3,5,6, are inputs, DIG OUT 2 is an
output and DIG IN OUT 4,7 ,8 are bidirectional. The software and the hardware of the radio model
define the function of each port.
DIG IN 1 can be used as external PTT input or others, set by the CPS. The 1-1P reads this port via pin
77 and 00171 .
DIG OUT 2 can be used as normal output or external alarm output, set by the CPS. Transistor
00173 is controlled by the 1-1P via ASFIC CMP, pin 14.
DIG IN 3 is read by IJP, pin 63 via resistor R0176
DIG IN 5 can be used as normal input or emergency input, set by the CPS. The 1-1P reads this port
via R0179 and 1-JP, pin 60. Diode D01791imits the voltage to protect the 1-1P input.
DIG IN 6 can be used as normal input, set by the CPS. The 1-1P reads this port via , pin 74 and
00181.
DIG IN OUT 4,7,8 are bidirectional and use the same circuit configuration. Each port uses an output
transistor 00177,00183,00185 controlled by JJP, pins46, 47, 53. The ports are read by IJP, pins 75,
54, 76. To use one of the ports as input the 1-1P must turn off the corresponding output transistor.
In addition the signals from DIG IN 1, DIG IN OUT 4 are fed to the option board connector J0551
and the expansion board connector J0451.