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MC100E016FN датащи(PDF) 8 Page - ON Semiconductor |
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MC100E016FN датащи(HTML) 8 Page - ON Semiconductor |
8 / 12 page MC10E016, MC100E016 http://onsemi.com 8 APPLICATIONS INFORMATION (continued) Programmable Divider The E016 has been designed with a control pin which makes it ideal for use as an 8−bit programmable divider. The TCLD pin (load on terminal count) when asserted reloads the data present at the parallel input pin (Pn’s) upon reaching terminal count (an all 1s state on the outputs). Because this feedback is built internal to the chip, the programmable division operation will run at very nearly the same frequency as the maximum counting frequency of the device. Figure 4 below illustrates the input conditions necessary for utilizing the E016 as a programmable divider set up to divide by 113. H L H H LLL H H H H TC PE CE TCLD CLK P7 P6 P4 P3 P2 P1 P0 P5 Q7 Q6 Q4 Q3 Q2 Q1 Q0 Q5 Figure 4. Mod 2 to 256 Programmable Divider To determine what value to load into the device to accomplish the desired division, the designer simply subtracts the binary equivalent of the desired divide ratio from the binary value for 256. As an example for a divide ratio of 113: Pn’s = 256 − 113 = 8F16 = 1000 1111 where: P0 = LSB and P7 = MSB Forcing this input condition as per the setup in Figure 4 will result in the waveforms of Figure 5. Note that the TC output is used as the divide output and the pulse duration is equal to a full clock period. For even divide ratios, twice the desired divide ratio can be loaded into the E016 and the TC output can feed the clock input of a toggle flip flop to create a signal divided as desired with a 50% duty cycle. Table 11. Preset Values for Various Divide Ratios Divide Ratio Preset Data Inputs P7 P6 P5 P4 P3 P2 P1 P0 2 H H H H H H H L 3 H H HHHH L H 4 H H HHHH L L 5 H H HHH L H H w w • ••••• • w • • ••••• • 112 H L L H LLL L 113 H L L L HHH H 114 H L L L HHH L • • • ••••• • • • • ••••• • 254 L L LLLL H L 255 L L LLLLL H 256 L L L L L L L L A single E016 can be used to divide by any ratio from 2 to 256 inclusive. If divide ratios of greater than 256 are needed multiple E016s can be cascaded in a manner similar to that already discussed. When E016s are cascaded to build larger dividers the TCLD pin will no longer provide a means for loading on terminal count. Because one does not want to reload the counters until all of the devices in the chain have reached terminal count, external gating of the TC pins must be used for multiple E016 divider chains. ••• PE ••• ••• Clock TC Load DIVIDE BY 113 Load 1001 0000 1001 0001 1111 1100 1111 1101 1111 1110 1111 1111 Figure 5. Divide by 113 E016 Programmable Divider Waveforms |
Аналогичный номер детали - MC100E016FN |
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