U.S. Traffic 170E-ATC - Peek Traffic

Chapter 4 — Hardware Programming InformationKeyboard Interfacethe modem and interrupt enables. See Table 2 and the Motorola manual forfurther details.The MPU can read the keyboard at any time by reading input port $5007. The keyboarddata is presented to the MPU as 4 bits of binary data to represent hexadecimal numbers0 to F and a control bit. These signals are debounced before being available at the inputport. Refer to Table 11 and Table 12 on page 24 for complete details of bit assignments.Display FunctionsThese are controlled by the MPU via output ports $5008, $5009 and $500A. Refer toTable 11 through Table 17, starting on page 24.Stop TimingThe state of this front panel toggle switch can be read by the MPU at input port address$5007 bit 6. Refer to Table 12 on page 25.Output PortsInput PortsThere are ten write only output ports located at addresses $5001 to $500A. Data writtento an output port by the MPU is latched there at the time of writing. The state of alloutput ports on power-up or at any time an RES signal occurs is an open circuit (logiczero). Refer to Table 13 through Table 17, starting on page 26, for details of bitassignments.There are 8 input ports located at addresses $5001 to $5008. These are read onlyports. Refer to Table 12 for complete details of all bit assignments.CPU Status PortThis is a read only port located at $5FFF. The status of all of the IRQ sources, addressconfiguration and DTA timeout can be read at this port. Refer to the “SystemAddressing Plan” on page 16 for complete details of all bit assignments.20 U.S. Traffic 170E-ATC Controller Operating Manual