AT89LP6440-20AU Atmel, AT89LP6440-20AU Datasheet - Page 15

• Manufacturer Part Number: AT89LP6440-20AU
• Description: MCU 8051 64K FLASH ISP 44TQFP
• Manufacturer: Atmel
• Series: 89LPr

Specifications of AT89LP6440-20AU

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 38
• Program Memory Size: 64KB (64K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 8K x 8
• Ram Size: 4.25K x 8
• Voltage - Supply (vcc/vdd): 2.4 V ~ 3.6 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Package: 44TQFP
• Device Core: 8051
• Family Name: 89LP
• Maximum Speed: 20 MHz
• Operating Supply Voltage: 2.5|3.3 V
• Data Bus Width: 8 Bit
• Number Of Programmable I/os: 38
• Interface Type: 2-Wire/SPI
• On-chip Dac: 8-chx10-bit
• Number Of Timers: 3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3706A–MICRO–9/09
Figure 3-6.
The auto-erase bit AERS (MEMCON.6) can be set to one to perform a page erase automatically
at the beginning of any write sequence. The page erase will erase the entire page, i.e. both the
low and high half pages. However, the write operation paired with the auto-erase can only pro-
gram one of the half pages. A second write cycle without auto-erase is required to update the
other half page.
Frequently just a few bytes within a page must be updated while maintaining the state of the
other bytes. There are two options for handling this situation that allow the Flash Data memory
to emulate a traditional EEPROM memory. The simplest method is to copy the entire page into a
buffer allocated in RAM, modify the desired byte locations in the RAM buffer, and then load and
write back first the low half page (with auto-erase) and then the high half page to the Flash mem-
ory. This option requires that at least one page size of RAM is available as a temporary buffer.
The second option is to store only one half page in RAM. The unmodified bytes of the other page
are loaded directly into the Flash memory’s temporary load buffer before loading the updated
values of the modified bytes. For example, if just the low half page needs modification, the user
must first store the high half page to RAM, followed by reading and loading the unaffected bytes
of the low half page into the page buffer. Then the modified bytes of the low half page are stored
to the page buffer before starting the auto-erase sequence. The stored value of the high half
page must be written without auto-erase after the programming of the low half page completes.
This method reduces the amount of RAM required; however, more software overhead is needed
because the read-and-load-back routine must skip those bytes in the page that need to be
updated in order to prevent those locations in the buffer from being loaded with the previous
data, as this will block the new data from being loaded correctly.
A write sequence will not occur if the Brown-out Detector is active, even if the BOD reset has
been disabled. In cases where the BOD reset is disabled, the user should check the BOD status
by reading the WRTINH bit in MEMCON. If a write currently in progress is interrupted by the
BOD due to a low voltage condition, the ERR flag will be set. FDATA can always be read regard-
less of the BOD state.
For more details on using the Flash Data Memory, see the application note titled “AT89LP Flash
Data Memory”. FDATA may also be programmed by an external device programmer (See
tion 25. on page
MWEN
DMEN
MOVX
LDPG
IDLE
FDATA Page Write
157).
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