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PIC18F23K22 Datasheet(PDF) 11 Page - Microchip Technology |
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PIC18F23K22 Datasheet(HTML) 11 Page - Microchip Technology |
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11 / 42 page  2010 Microchip Technology Inc. Advance Information DS41398B-page 11 PIC18(L)F2XK22/4XK22 2.6 Entering and Exiting Low-Voltage ICSP Program/Verify Mode Low-voltage entry into ICSP modes for PIC18(L)F2XK22/4XK22 devices is somewhat different than previous PIC18 devices. As shown in Figure 2-14, entering ICSP Program/Verify mode requires three steps: 1. Voltage is briefly applied to the MCLR pin. 2. A 32-bit key sequence is presented on PGD. 3. Voltage is reapplied to MCLR. The programming voltage applied to MCLR is VIH, or usually, VDD. There is no minimum time requirement for holding at VIH. After VIH is removed, an interval of at least P18 must elapse before presenting the key sequence on PGD. The key sequence is a specific 32-bit pattern, ‘0100 1101 0100 0011 0100 1000 0101 0000’ (more easily remembered as 4D434850h in hexa- decimal). The device will enter Program/Verify mode only if the sequence is valid. The Most Significant bit of the most significant nibble must be shifted in first. Once the key sequence is complete, VIH must be applied to MCLR and held at that level for as long as Program/Verify mode is to be maintained. An interval of at least time P20 and P15 must elapse before present- ing data on PGD. Signals appearing on PGD before P15 has elapsed may not be interpreted as valid. On successful entry, the program memory can be accessed and programmed in serial fashion. While in the Program/Verify mode, all unused I/Os are placed in the high-impedance state. Exiting Program/Verify mode is done by removing VIH from MCLR, as shown in Figure 2-15. The only requirement for exit is that an interval, P16, should elapse between the last clock and the program signals on PGC and PGD before removing VIH. When VIH is reapplied to MCLR, the device will enter the ordinary operational mode and begin executing the application instructions. FIGURE 2-14: ENTERING LOW-VOLTAGE PROGRAM/VERIFY MODE FIGURE 2-15: EXITING LOW-VOLTAGE PROGRAM/VERIFY MODE MCLR PGD PGC VDD P13 b31 b30 b29 b28 b27 b2 b1 b0 b3 ... Program/Verify Entry Code = 4D434850h P2B P2A P18 P20 0 1 001 000 0 P15 VIH VIH MCLR P16 PGD PGC VDD VIH VIH PGD = Input |
Similar Part No. - PIC18F23K22 |
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Similar Description - PIC18F23K22 |
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