Datasheet

AVR068
29
2591C-AVR-06/06
5.7.6 PARAM_VTARGET
This parameter only applies to STK500, not the AVRISP.
STK500 has a controllable target voltage supply, which can be set and monitored with
this parameter. The parameter value is voltage in volts x10, i.e. a parameter value of
42 (decimal) corresponds to 4.2V. The VTARGET voltage is adjustable between 0
and 6V.
5.7.7 PARAM_VADJUST
This parameter only applies to STK500, not the AVRISP.
STK500 has an adjustable analog reference in the same way as the supply voltage.
This adjustable reference voltage (AREF) can be set and monitored with the
PARAM_ADJUST parameter. The parameter value is voltage in volts x10, i.e. a
parameter value of 42 (decimal) corresponds to 4.2V. The VADJUST voltage is
adjustable between 0 and 6V.
5.7.8 PARAM_OSC_PSCALE
This parameter only applies to STK500, not the AVRISP.
The STK500 has a programmable clock generator used to supply a clock signal to the
target device. The generator is actually the TIMER2 of the AT90S8535 MCU. The
timer in running in “Toggle OC2 line” mode, where the timer value is cleared on a
compare match. The following code example shows how the firmware handles
changes in PARAM_OSC_PSCALE or PARAM_OSC_CMATCH:
// Stop Timer2
TCCR2 = 0x18;
// Initialize counter value
TCNT2 = 0xFF;
// Set compare match value
OCR2 = osc_cmatch;
// Set timer operation mode and prescaler
TCCR2 = (0x18 | (0x07 & osc_pscale));