ZBasicSysLib - page 23 of 323

ZBasic System Library

ZX Microcontroller Family

ZX devices have three or more timers, depending on the underlying CPU type, that are used for various

purposes. One of the timers is used to implement the real time clock (RTC), another is used for the

software-based serial ports and a third timer is used to provide the precise timing required for certain I/O

routines. The specific timer that is used for a particular function varies depending on the underlying CPU

type as shown in the table below.

Timer Usage by CPU Type

InputCapture OutputCapture

mega32, mega328P,

mega644, mega644P

The RTC Timer is programmed to generate an interrupt that is used to update the RTC and to trigger task

switching. Because its role is so central, the RTC Timer cannot be used for any other purpose. The I/O

Timer is used by several I/O related routines as explained in more detail below. The Serial Timer is used

to generate interrupts to implement the timing required for serial channels Com3 to Com6. If none of the

channels 3-6 is open, the Serial Port Timer can be used for other purposes in your program. Timers are