To enter Program/Verify mode via the VPP-First Entry mode, the following sequence must be followed:
- 1.Hold ICSPCLK and ICSPDAT low.
- 2.Raise the voltage on MCLR from 0V to VIHH.
- 3. Raise the voltage on VDD from 0V to the desired operating voltage.
The VPP-First Entry mode prevents the device from executing code prior to
entering the Program/Verify mode. For example, when the Configuration Byte has already
been programmed to have MCLR disabled (MCLRE =
0), the Power-up Timer disabled (PWRTE =
0) and the internal oscillator selected, the device will execute
the code immediately. VPP-First Entry mode is strongly recommended as it
prevents the user code from executing. See the timing diagram in Figure 1.
Figure 1. Programming Entry and Exit Modes –
VPP-First and Last
