33.6.1 Signal Names

In this section, some pins of this device are referenced by signal names describing their functionality during parallel programming. Refer to the figure Parallel Programming and to the table Pin Name Mapping below. Pins not described in the following table are referenced by pin names.

The XA1/XA0 pins determine the action executed when the XTAL1 pin is given a positive pulse. The bit coding is shown in the table XA1 and XA0 Coding below.

When pulsing WR or OE, the command loaded determines the action executed. The different commands are shown in the table Command Byte Bit Coding below.

Figure 33-1. Parallel Programming

Note: VCC - 0.3V < AVCC < VCC + 0.3V; however, AVCC should always be within 4.5 - 5.5V

Table 33-12. Pin Name Mapping
Signal Name in Programming ModePin NameI/OFunction
RDY/BSYPD1O0: Device is busy programming, 1: Device is ready for new command
OEPD2IOutput Enable (Active low)
WRPD3IWrite Pulse (Active low)
BS1PD4IByte Select 1 (“0” selects Low byte, “1” selects High byte)
XA0PD5IXTAL Action Bit 0
XA1PD6IXTAL Action Bit 1
PAGELPD7IProgram memory and EEPROM Data Page Load
BS2PC2IByte Select 2 (“0” selects Low byte, “1” selects 2’nd High byte)
DATA{PC[1:0]: PB[5:0]}I/OBi-directional Data bus (Output when OE is low)
Table 33-13. Pin Values Used to Enter Programming Mode
PinSymbolValue
PAGELProg_enable[3]0
XA1Prog_enable[2]0
XA0Prog_enable[1]0
BS1Prog_enable[0]0
Table 33-14. XA1 and XA0 Coding
XA1XA0Action when XTAL1 is Pulsed
00Load Flash or EEPROM Address (High or low address byte determined by BS1)
01Load Data (High or Low data byte for Flash determined by BS1)
10Load Command
11No Action, Idle
Table 33-15. Command Byte Bit Coding
Command ByteCommand Executed
1000 0000Chip Erase
0100 0000Write Fuse bits
0010 0000Write Lock bits
0001 0000Write Flash
0001 0001Write EEPROM
0000 1000Read Signature Bytes and Calibration byte
0000 0100Read Fuse and Lock bits
0000 0010Read Flash
0000 0011Read EEPROM