Mode 1, Mode 2, Mode 1 -5 – Maxim Integrated Ultra-High-Speed Flash Microcontroller User Manual

Page 125: Mode 2 -5

11-5

Mode 1

Mode 1 configures the timer for 16-bit operation as either a timer or counter. Figure 11-1 shows that setting the TMOD select bits M1,

M0 = 01b invoke this operating mode. For timer n, all of the TLn and THn registers are used. For example, if timer 1 is configured in

mode 1, then TL1 holds the LSB and TH1 holds the MSB. Rollover occurs when the timer reaches FFFFh. An interrupt also occurs if

enabled and the relevant TFn flag is set. Time-base selection, counter/timer selection, and the gate function operate as described in

mode 0.

Mode 2

This mode configures the timer as an 8-bit timer/counter with automatic reload of the start value. This configuration is shown in Figure

11-2, and is selected when bits M1and M0 of the TCON register are set to 1 and 0, respectively. When configured in mode 2, the timer

uses TLn to count and THn to store the reload value. Software must initialize both TLn and THn with the same starting value for the first

count to be correct. Once the TLn reaches FFh, it is automatically loaded with the value in THn. The THn value remains unchanged

unless modified by software. Mode 2 is commonly used to generate baud rates since it runs without continued software intervention.

As in modes 0 and 1, mode 2 allows counting of either clock cycles or pulses on pin Tn (C/T = 1) when counting is enabled by TRn

and the proper setting of GATE and INTn pins.

MODE 0

M1, M0 = TMOD.1,

TMOD.0

(M1, M0 = TMOD.5,

TMOD.4)

MODE 1

INPUT TO TIMER

CLK MODE

SYSCLK

DIVIDE-BY-1 OSC / 1

OSC / 0.25

OSC / 0.5

DIVIDE-

BY-12

DIVIDE-

BY-4

T0 = P3.4

(T1 = P3.5)

TR0 = TCON.4

(TR1 = TCON.6)

GATE = TMOD.3

(GATE = TMOD.7)

INT0 = P3.2

( INT1 = P3.3)

TF0 = TCON.5

(TF1 = TCON.7)

TIMER 1 FUNCTIONS

SHOWN IN PARENTHESES ()

INTERRUPT

TL0

(TL1)

TH0

(TH1)

CLK

T0M = CKCON.3

(T1M = CKCON.4)

C / T = TMOD.2

(C / T = TMOD.6)

EXTERNAL OSCILLATOR

T0MH = CKMOD.3

(T1MH = CKMOD.4)

NOTE: FOR POWER-MANAGEMENT MODE (DIVIDE-BY-1024) OPERATION, THE TIMER INPUT CLOCK TO THE TIMER IS

OSC / 1024 IF EITHER TXM = 1 OR TXMH = 1. OTHERWISE, THE TIMER INPUT IS OSC / 3072.

Figure 11-1. Timers/Counters 0 and 1, Modes 0 and 1

Ultra-High-Speed Flash
Microcontroller User’s Guide

Maxim Integrated