Question

Which is the operation for mode 2?

(a) 13-bit timer mode, 8-bit timer/counter THx and TLx as 5-bit prescalar

(b) 16-bit timer mode, 16-bit timer/counter THx and TLx are cascaded, no prescalar

(c) 8-bit auto reload mode, 8-bit auto reload time/counter; THx holds a value which is to be reloaded into TLx each time it overflows

(d) Spilt timer mode

This question was addressed to me during an interview for a job.

This intriguing question comes from Microcontroller (8051- Pin, Registers, Timers) in portion Prototyping Embedded Devices of IOT

Answer 1

Correct choice is (c) 8-bit auto reload mode, 8-bit auto reload time/counter; THx holds a value which is to be reloaded into TLx each time it overflows

Easiest explanation: It is an 8 bit timer that allows only values of 00 to FFH to be loaded into the timer’s register TH. After TH is loaded with 8 bit value, 8051 gives a copy of it to TL.