AT89LP428-20MU ATMEL [ATMEL Corporation], AT89LP428-20MU Datasheet - Page 115

• Manufacturer Part Number: AT89LP428-20MU
• Description: 8-bit Microcontroller with 4K/8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

23. Programming the Flash Memory
23.1
3654A–MICRO–8/09
Physical Interface
The Atmel AT89LP428/828 microcontroller features 4K/8K bytes of on-chip In-System Program-
mable Flash program memory and 512/1024 bytes of nonvolatile Flash data memory. In-System
Programming allows programming and reprogramming of the microcontroller positioned inside
the end system. Using a simple 4-wire SPI interface, the programmer communicates serially
with the AT89LP428/828 microcontroller, reprogramming all nonvolatile memories on the chip.
In-System Programming eliminates the need for physical removal of the chips from the system.
This will save time and money, both during development in the lab, and when updating the soft-
ware or parameters in the field. The programming interface of the AT89LP428/828 includes the
following features:
For more detailed information on In-System Programming, refer to the Application Note entitled
“AT89LP In-System Programming Specification”.
Flash Programming utilizes the Serial Peripheral Interface (SPI) pins of an AT89LP428/828
microcontroller. The SPI is a full-duplex synchronous serial interface consisting of four wires:
Serial Clock (SCK), Master-in/Slave-out (MISO), Master-out/Slave-in (MOSI), and an active-low
Slave Select (SS). When programming an AT89LP428/828 device, the programmer always
operates as the SPI master, and the target system always operates as the SPI slave. To enter or
remain in Programming mode the device’s reset line (RST) must be held active (low). With the
addition of VCC and GND, an AT89LP428/828 microcontroller can be programmed with a mini-
mum of seven connections as shown in
Figure 23-1. In-System Programming Device Connections
• 4-wire SPI Programming Interface
• Active-low Reset Entry into Programming
• Slave Select Allows Multiple Devices on Same Interface
• User Signature Array
• Flexible Page Programming
• Row Erase Capability
• Page Write with Auto-Erase Commands
• Programming Status Register
Serial Clock
Serial Out
Serial In
SS
Figure
P1.7/SCK
P1.6/MISO
P1.5/MOSI
P1.4/SS
GND
AT89LP428/LP828
23-1.
P3.6/RST
VCC
AT89LP428/828
RST
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