Pin Descriptions If an external signal source is used instead of the internal oscillator, it should be connected to the RS input and the RTC and CTC pins should be left open. TETransmit Enable (Pin 14) This active-low transmit enable input initiates transmission when forced low. An internal pull-up device keeps this input normally high. The pull-up current is specified in the Electrical Characteristics table. DoutData Out (Pin 15) This is the output of the encoder that serially presents the encoded data word. VSSNegative Power Supply (Pin 8) The most-negative supply potential. This pin is usually ground. VDDPositive Power Supply (Pin 16) The most-positive power supply pin. 4.2MC145027 and MC145028 DecodersA1 - A5, A1 - A9Address Inputs (Pins 1 - 5) - MC145027,Address Inputs (Pins 1 - 5, 15, 14, 13, 12) - MC145028 These are the local address inputs. The states of these pins must match the appropriate encoder inputs for the VT pin to go high. The local address may be encoded with trinary or binary data. D6 - D9Data Outputs (Pins 15, 14, 13, 12) - MC145027 Only These outputs present the binary information that is on encoder inputs A6/D6 through A9/D9. Only binary data is acknowledged; a trinary open at the MC145026 encoder is decoded as a high level (logic 1). DinData In (Pin 9) This pin is the serial data input to the decoder. The input voltage must be at CMOS logic levels. The signal source driving this pin must be dc coupled. MC145026, MC145027, MC145028 Technical Data, Rev. 4 10 Freescale Semiconductor Document Outline 1 Introduction 2 Electrical Specifications 3 Operating Characteristics 3.1 MC145026 3.2 MC145027 3.3 MC145028 4 Pin Descriptions 4.1 MC145026 Encoder 4.2 MC145027 and MC145028 Decoders 5 MC145027 and MC145028 Timing 6 Package Dimensions
