AT89LP428 datasheet(115/149 Pages) ATMEL

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115

3654A–MICRO–8/09

AT89LP428/828

23. Programming the Flash Memory

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:

• 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

For more detailed information on In-System Programming, refer to the Application Note entitled

“AT89LP In-System Programming Specification”.

23.1

Physical Interface

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.

Figure 23-1. In-System Programming Device Connections

AT89LP428/LP828

VCC

P3.6/RST

P1.7/SCK

P1.5/MOSI

GND

Serial Clock

Serial In

RST

P1.4/SS

P1.6/MISO

Serial Out

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