AT89LP6440 datasheet(156/194 Pages) ATMEL

156 / 194 page

156

3706A–MICRO–9/09

AT89LP6440 - Preliminary

• P4.2/RST cannot be connected directly to V

DD and any external capacitors connected to RST

must be removed.

• All external reset sources must be removed.

• If P4.3 needs to be debugged in systems using the crystal oscillator, the external clock option

should be selected. The quartz crystal and any capacitors on XTAL1 or XTAL2 must be

removed and an external clock signal must be driven on XTAL1. Some emulator systems may

provide a user-configurable clock for this purpose.

Figure 24-1. AT89LP6440 On-Chip Debug Connections

24.2

Software Breakpoints

The AT89LP6440 microcontroller includes a BREAK instruction for implementing program mem-

ory breakpoints in software. A software breakpoint can be inserted manually by placing the

BREAK instruction in the program code. Some emulator systems may allow for automatic inser-

tion/deletion of software breakpoints. The Flash memory must be re-programmed each time a

software breakpoint is changed. Frequent insertions/deletions of software breakpoints will

reduce the endurance of the nonvolatile memory. Devices used for debugging purposes should

not be shipped to end customers. The BREAK instruction is treated as a two-cycle NOP when

OCD is disabled.

24.3

Limitations of On-Chip Debug

The AT89LP6440 is a fully-featured microcontroller that multiplexes several functions on its lim-

ited I/O pins. Some device functionality must be sacrificed to provide resources for On-Chip

Debugging. The On-Chip Debug System has the following limitations:

•The Debug Clock pin (DCL) is physically located on that same pin as Port Pin P4.2 and the

External Reset (RST). Therefore, neither P4.2 nor an external reset source may be emulated

when OCD is enabled.

CLK = Internal RC

VDD

XTAL1

P4.2/RST

GND

DCL

DDA

CLK = External Clock

VDD

XTAL2

P4.2/RST

GND

DCL

DDA

XTAL1

CLK

CLK = Crystal Oscillator

VDD

P4.3

P4.2/RST

GND

DCL

DDA

XTAL1

XTAL2

AT89LP6440 Datasheet(PDF) 156 Page - ATMEL Corporation

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