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DBAT90USB162 Enhanced
Development Board User’s Manual
2.2. SCHEMATIC DESCRIPTION AND CONFIGURATION
2.2.1. Clock
Depending on jumper configuration clock source is either internal from 0.9..16
MHz
(1)
crystal oscillator, or internal calibrated RC oscillator, or external
(2)
via
EXTCLK (P2). For using external clock CKSEL fuses must be programmed (see
AT90USB162 datasheet).
Clock
J1
J2
J3
J4
Internal crystal
open
short short
open
External
short
open
open
short
Note:
1. Default is 8 MHz crystal, other is possible by request.
2. XTAL2 (PC0) can be used as generic I/O depending on MCU
configuration.
2.2.2. Reset button (S2)
Cold reset is done either manually by RST button (S2) or externally via RSTDW
(P11, P21-27).
Optionally a parallel capacitor (C5) can be installed to the RST button (S2). The
PCB accepts thru-hole and 0805 SMD.
2.2.3. HWB button (S1)
The hardware boot button allows forcing bootloader execution after reset (see
AT90USB162 datasheet) thus allowing MCU programming via USB without
external programmer. The HWB mode is active only when the HWBE fuse is
enabled. In that case PD7/HWB pin is configured as input during reset and
sampled during reset rising edge.
Optionally a parallel capacitor (C4) can be installed. The PCB accepts thru-hole
and 0805 SMD.
