Rainbow Electronics AT90LS8535 - Manual (Page 98)

98
AT90S/LS8535
1041H–11/01
Programming the Fuse Bits The algorithm for programming the Fuse bits is as follows (refer to “Programming the
Flash” for details on command and data loading):
1. A: Load Command “0100 0000”.
2. D: Load Data Low Byte. Bit n = “0” programs and bit n = “1” erases the Fuse bit.
Bit 5 = SPIEN Fuse bit.
Bit 0 = FSTRT Fuse bit.
Bit 7-6,4-1 = “1”. These bits are reserved and should be left unprogrammed (“1”).
3. Give WR a t
WLWH_PFB
-wide negative pulse to execute the programming, t
WLWH_PFB
is found in Table 40. Programming the Fuse bits does not generate any activity
on the RDY/BSY pin.
Programming the Lock Bits The algorithm for programming the Lock bits is as follows (refer to “Programming the
Flash” on page 95 for details on command and data loading):
1. A: Load Command “0010 0000”.
2. D: Load Data Low Byte. Bit n = “0” programs the Lock bit.
Bit 2 = Lock Bit2
Bit 1 = Lock Bit1
Bit 7-3,0 = “1”. These bits are reserved and should be left unprogrammed (“1”).
3. E: Write Data Low Byte.
The Lock bits can only be cleared by executing Chip Erase.
Reading the Fuse and Lock
Bits The algorithm for reading the Fuse and Lock bits is as follows (refer to “Programming
the Flash” on page 95 for details on command loading):
1. A: Load Command “0000 0100”.
2. Set OE to “0” and BS to “1”. The status of the Fuse and Lock bits can now be
read at DATA (“0” means programmed).
Bit 7 = Lock Bit1
Bit 6 = Lock Bit2
Bit 5 = SPIEN Fuse bit
Bit 0 = FSTRT Fuse bit
3. Set OE to “1”.
Observe that BS needs to be set to “1”.
Reading the Signature Bytes The algorithm for reading the signature bytes is as follows (refer to “Programming the
Flash” on page 95 for details on command and address loading):
1. A: Load Command “0000 1000”.
2. C: Load Address Low Byte ($00 - $02).
Set OE to “0” and BS to “0”. The selected signature byte can now be read at DATA.
3. Set OE to “1”.