PIC Development Systems 157 PICkitX and ICDX programmers are both capable of supporting ICD. Unfortunately, the smaller mid-range (16FXXX) chips, including the 16F690 chip fitted in the LPC board, do not support ICD internally, owing to pin-out limitations and cost constraints. For these chips, ICD can be implemented instead by using a header board connected between the ICD module and the chip socket on the application board. The header board carries a version of the target chip that incorporates the on-chip ICD circuitry, which substitutes for the target device while the system is under development (these chips are not available separately). The ICD header system configuration is shown in Figure 7.5(a). The ICD module sits in between the host PC running MPLAB IDE and the application board MCU socket (Figure 7.5b). When debugging is complete, the chip can be programmed to run independently and plugged directly into the board. The ICD signals are shown in Figure 7.5(c), with definitions provided in Table 7.1. The on-board reset circuit has been included to show how it is isolated from the V PP by a 1k0 resistor. 7.10. In-Circuit Emulation