ZBasicSysLib - page 313 of 323

ZBasic System Library

ZX Microcontroller Family

By default, each pin that is enabled for a pin change interrupt will trigger the interrupt on either edge. You

may configure the sensitivity for each individual pin to trigger an interrupt on either edge, rising edge only,

falling edge only or a low level. The setting for each pin change sensitivity is made in a “pin control”

register specific to that pin. For example, the pin control register for bit 3 of port C is named

PORTC_PIN3CTRL. Consult the ATxmega A datasheet for more information on these registers.

Analog Comparator Interrupt (ATmega-based devices)

A task may await an analog comparator interrupt by specifying the value &H10 for intNum. The

corresponding built-in constant is waitAnalogComp. In this case, the mode parameter specifies the

comparator output transition that will cause the interrupt to occur.

Analog Comparator Interrupt Mode Values

Built-in Constant

Interrupt Trigger

zxAnalogCompChange

Comparator output rising edge or falling edge.

zxAnalogCompFalling

Comparator output falling edge.

zxAnalogCompRising

Comparator output rising edge.

With all of the mode values in the table above, the analog comparator’s positive input is AIN0 (Port B, bit

2) and the comparator’s negative input is either AIN1 (Port B, bit 3) or, if the ACME bit is set in a CPU

register (see below), the analog input specified by the multiplexor select bits in Register.ADMUX. On the

ZX-24 models, AIN0 is common with Port A, bit 2 so the latter I/O pin will need to be configured to be an

input in high-impedance mode. Also, on the ZX-24 models built using boards earlier than Rev 5 (see the

bottom side of the board), AIN1 has no external connection so the negative input must be supplied via the

analog multiplexor. The ACME bit is in Register.SFIOR for the mega32 and mega128-based ZX models

and in Register.ADCSRB in the mega644, mega644P, mega1284P, mega1280 and mega1281-based

Another option for the positive comparator input is to select the internal “band gap” voltage. This voltage

level (approximately 1.23 volts) is selected by adding &H40 to the mode values in the table above. The

built-in constant zxAnalogReference has this value.

See the section in the Atmel microcontroller documentation describing the analog comparator for further

Analog Comparator Interrupt (ATxmega-based devices)

A task may await an analog comparator interrupt on one of the analog comparator channels by specifying

the corresponding value shown in the table below for intNum.

Analog Comparator Interrupt Number Values

Built-in Constant

Interrupt Trigger

waitAnalogCompA0

Analog Comp A, Channel 0

xmega128A1, xmega32A4

WaitAnalogCompA1

Analog Comp A, Channel 1

xmega128A1, xmega32A4

waitAnalogCompAW

Analog Comp A, Window mode

xmega128A1, xmega32A4

waitAnalogCompB0

Analog Comp B, Channel 0

WaitAnalogCompB1

Analog Comp B, Channel 1

waitAnalogCompBW

Analog Comp B, Window mode

In order to use any of the analog comparator interrupts, you must first configure positive and negative

inputs to the corresponding comparator(s) using the processor registers ACA_AC0MUXCTRL,

ACA_AC1MUXCTRL, ACB_AC0MUXCTRL and/or ACB_AC1MUXCTRL. Also, the high speed/low power

control bit and the hysteresis control bits in the ACA_AC0CTRL, ACA_AC1CTRL, ACB_AC0CTRL and

ACB_AC1CTRL registers may be configured as desired before invoking WaitForInterrupt(). Consult the

ATxmega A datasheet for more information on these registers.