29.6.1 Signal Names

In this section, some pins of this device are referenced by signal names describing their functionality during parallel programming, please refer to the following figure and table Pin Name Mapping in this section. 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 in this section.

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

Table 29-8. Pin Name Mapping
Signal Name in Programming Mode	Pin Name	I/O	Function
RDY/BSY	PD1	O	0: Device is busy programming, 1: Device is ready for new command
OE	PD2	I	Output Enable (Active low)
WR	PD3	I	Write Pulse (Active low)
BS1	PD4	I	Byte Select 1 (“0” selects Low byte, “1” selects High byte)
XA0	PD5	I	XTAL Action Bit 0
XA1	PD6	I	XTAL Action Bit 1
PAGEL	PD7	I	Program memory and EEPROM Data Page Load
BS2	PC2	I	Byte Select 2 (“0” selects Low byte, “1” selects 2’nd High byte)
DATA	{PC[1:0]: PB[5:0]}	I/O	Bi-directional Data bus (Output when OE is low)

Table 29-9. Pin Values Used to Enter Programming Mode
Pin	Symbol	Value
PAGEL	Prog_enable[3]	0
XA1	Prog_enable[2]	0
XA0	Prog_enable[1]	0
BS1	Prog_enable[0]	0

Table 29-10. XA1 and XA0 Coding
XA1	XA0	Action when XTAL1 is Pulsed
0	0	Load Flash or EEPROM Address (High or low address byte determined by BS1)
0	1	Load Data (High or Low data byte for Flash determined by BS1)
1	0	Load Command
1	1	No Action, Idle

Table 29-11. Command Byte Bit Coding
Command Byte	Command Executed
1000 0000	Chip Erase
0100 0000	Write Fuse bits
0010 0000	Write Lock bits
0001 0000	Write Flash
0001 0001	Write EEPROM
0000 1000	Read Signature Bytes and Calibration byte
0000 0100	Read Fuse and Lock bits
0000 0010	Read Flash
0000 0011	Read EEPROM