Manual

94
AT90S/LS8535
1041H–11/01
Enter Programming Mode The following algorithm puts the device in Parallel Programming Mode:
1. Apply supply voltage according to Table 36, between V
CC
and GND.
2. Set the RESET and BS pin to “0” and wait at least 100 ns.
3. Apply 11.5 - 12.5V to RESET. Any activity on BS within 100 ns after +12V has
been applied to RESET
, will cause the device to fail entering programming mode.
Table 37. 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)
BS PD4 I
Byte Select (“0” selects low byte, “1” selects high
byte)
XA0 PD5 I XTAL Action Bit 0
XA1 PD6 I XTAL Action Bit 1
DATA PB7 - 0 I/O Bi-directional Data Bus (Output when OE
is low)
Table 38. 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 BS)
0 1 Load Data (High or low data byte for Flash determined by BS)
1 0 Load Command
1 1 No Action, Idle
Table 39. 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
0000 0100 Read Lock and Fuse Bits
0000 0010 Read Flash
0000 0011 Read EEPROM