Specifications

165
3706C–MICRO–2/11
AT89LP3240/6440
25.8 User Signature and Analog Configuration
The User Signature Array contains 256 bytes of non-volatile memory in two 128-byte pages. The
first page of the User Signature Array (0000H–007FH) is available for serial numbers, firmware
revision information, date codes or other user para meters. The User Signature Array may only
be written by an external device when the U
ser Signature Programming Fuse is enabled. When
the fuse is enabled, Chip Erase will also erase the first page of the array. When the fuse is dis-
abled, the array is not affected by write or erase commands. Programming of the Signatu re
Array can also be disabled by the Lock Bits. However, reading the signature is alwa
ys allowed
and the array should not be used to store security sensitive informa tion. The User Signature
Array may be modified during execution through the In-Application Programming interface,
regardless of the state of the User Signature Programming fus e or Lock Bits, provided that the
IAP Fuse is enabled. Note that the address of the User Signa
ture Array, as seen by the IAP
interface, equals the User Signature address plus 256 (0100H–01FFH instead of 0000H–
00FFH).
The second page of the User Signature Arra y (0080H–00FFH) contains analog configuration
parameters for the AT89LP3240/6440. Each byte represents a parameter as listed in Table 25-6
and is pres
et in the factory. The parameters are read at POR a nd the device is configured
accordingly. The second page of the array is not affected by Chip Erase. Other bytes in this
page may be used as additional signature space; however, care should be taken to preserve the
parameter values when modifying other bytes.
25.9 Programming Interface Timing
This section details general system timing sequences and constra ints for entering or exiting In-
System Programming as well as parameters related to the Serial Peripheral Interface during
ISP. The general timing parameters for the following waveform figures are listed in section “Tim-
ing Parameters” on page 169.
25.9.1 Power-up Sequence
Execute this sequence to enter progr
amming mode immediately after power-up. In the RST pin
is disabled or if the ISP Fus e is disabled, this is the only method to enter programming (see
“External Reset” on page 35).
1. Apply power between VDD and GND pins. RST
should remain low.
2. Wait at least t
PWRUP
. and drive SS high.
3. Wait at least t
SUT
for the internal Power-on Reset to complete. The value of t
SUT
will
depend on the current settings of the device.
4. Start programming session.
Table 25-6. Analog Configuration Definitions
Address Parameter Name Description
0080H RC Oscillator Calibration Byte
The RC Calibration Byte controls the frequency of the internal RC oscillator. The
frequency is inversely proportional to the calibration value such that higher values
result in lower frequencies. A copy of the factory-set calibration value is stored at
location 0008H of the Atmel Signature.