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.

Figure 1. Parallel Programming
Table 1. 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 2. 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 3. 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 4. 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