PIC18F2XXX/4XXX FAMILY
DS30009622M-page 18 2010-2015 Microchip Technology Inc.
2.7 Serial Program/Verify Operation
The PGC pin is used as a clock input pin and the PGD pin is used for entering command bits and data input/output
during serial operation. Commands and data are transmitted on the rising edge of PGC, latched on the falling edge of
PGC and are Least Significant bit (LSb) first.
2.7.1 4-BIT COMMANDS
All instructions are 20 bits, consisting of a leading 4-bit command followed by a 16-bit operand, which depends on the type
of command being executed. To input a command, PGC is cycled four times. The commands needed for programming
and verification are shown in Table 2-8.
Depending on the 4-bit command, the 16-bit operand represents 16 bits of input data or 8 bits of input data and 8 bits
of output data.
Throughout this specification, commands and data are presented as illustrated in Table 2-9. The 4-bit command is shown
Most Significant bit (MSb) first. The command operand, or “Data Payload”, is shown as <MSB><LSB>. Figure 2-18
demonstrates how to serially present a 20-bit command/operand to the device.
2.7.2 CORE INSTRUCTION
The core instruction passes a 16-bit instruction to the CPU core for execution. This is needed to set up registers as
appropriate for use with other commands.
TABLE 2-8: COMMANDS FOR PROGRAMMING
TABLE 2-9: SAMPLE COMMAND SEQUENCE
Description 4-Bit Command
Core Instruction
(Shift in16-bit instruction)
0000
Shift Out TABLAT Register 0010
Table Read 1000
Table Read, Post-Increment 1001
Table Read, Post-Decrement 1010
Table Read, Pre-Increment 1011
Table Write 1100
Table Write, Post-Increment by 2 1101
Table Write, Start Programming,
Post-Increment by 2
1110
Table Write, Start Programming 1111
4-Bit Command Data Payload Core Instruction
1101 3C 40 Table Write,
post-increment by 2
