Datasheet MC145026, MC145027, MC145028 (NXP) - 8

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Operating Characteristics
90% tf tf ANY OUTPUT VDD 10% 90% Din t 10% TLH tTHL VSS
Figure 5. Output Transition Time Figure 6. Din Rise and Fall Time
t/fOSC VDD TE 50% VSS R 50% TC tW
Figure 7. Encoder Clock Frequency Figure 8. TE Pulse Width
TEST POINT OUTPUT DEVICE UNDER TEST CL* * Includes all probe and fixture capacitance.
Figure 9. Test Circuit 3 Operating Characteristics 3.1 MC145026
The encoder serially transmits trinary data as defined by the state of the A1 - A5 and A6/D6 - A9/D9 input pins. These pins may be in either of three states (low, high, or open) allowing 19,683 possible codes. The transmit sequence is initiated by a low level on the TE input pin. Upon power-up, the MC145026 can continuously transmit as long as TE remains low (also, the device can transmit two-word sequences by pulsing TE low). However, no MC145026 application should be designed to rely upon the first data word transmitted immediately after power-up because this word may be invalid. Between the two data words, no signal is sent for three data periods (see Figure 11). Each transmitted trinary digit is encoded into pulses (see Figure 12). A logic 0 (low) is encoded as two consecutive short pulses, a logic 1 (high) as two consecutive long pulses, and an open (high impedance) as a long pulse followed by a short pulse. The input state is determined by using a weak “output” device to try to force each input high then low. If only a high state results from the two tests, the input is assumed to be hardwired to VDD. If only a low state is obtained, the input is assumed to be hardwired to VSS. If both a high and a low can be forced at an input, an open is assumed and is encoded as such. The “high” and
MC145026, MC145027, MC145028 Technical Data, Rev. 4
8 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