Rainbow-electronics AT90LS2343 Manual de usuario descargar pdf (Pagina 5)

AT90S/LS2323/2343

1004D–09/01

Pin Descriptions

AT90S/LS2343

VCC Supply voltage pin.

GND Ground pin.

Port B (PB4..PB0) Port B is a 5-bit bi-directional I/O port with internal pull-up resistors. The Port B output

buffers can sink 20 mA. As inputs, Port B pins that are externally pulled low, will source

current if the pull-up resistors are activated.

Port B also serves the functions of various special features.

Port pins can provide internal pull-up resistors (selected for each bit). The Port B pins

are tri-stated when a reset condition becomes active.

RESET

Reset input. An external reset is generated by a low level on the RESET pin. Reset

pulses longer than 50 ns will generate a reset, even if the clock is not running. Shorter

pulses are not guaranteed to generate a reset.

CLOCK Clock signal input in external clock mode.

Clock Options

Crystal Oscillator The AT90S/LS2323 contains an inverting amplifier that can be configured for use as an

On-chip oscillator, as shown in Figure 3. XTAL1 and XTAL2 are input and output

respectively. Either a quartz crystal or a ceramic resonator may be used. It is recom-

mended that the AT90S/LS2343 be used if an external clock source is used, since this

gives an extra I/O pin.

Figure 3. Oscillator Connection

External Clock The AT90S/LS2343 can be clocked by an external clock signal, as shown in Figure 4, or

by the On-chip RC oscillator. This RC oscillator runs at a nominal frequency of 1 MHz

= 5V). A fuse bit (RCEN) in the Flash memory selects the On-chip RC oscillator as

the clock source when programmed (“0”). The AT90S/LS2343 is shipped with this bit

programmed. The AT90S/LS2343 is recommended if an external clock source is used,

because this gives an extra I/O pin.

The AT90S/LS2323 can be clocked by an external clock as well, as shown in Figure 4.

No fuse bit selects the clock source for AT90S/LS2323.

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