SM89516B datasheet(30/49 Pages) SYNCMOS

30 / 49 page

SM89516B

8-Bit Micro-controller

64KB Flash

& 1KB RAM embedded

Specifications subject to change without notice contact your sales representatives for the most recent information.

ISSFD-M087

Ver D SM89516B 08/07/2015

- 30 -

EXEN2: Timer 2 external enable bit. When set, allows a capture or reload to occur as a result of a

negative transition on T2EX if Timer 2 is not being used to clock the serial port. EXEN2 =

0 causes Timer 2 to ignore events at T2EX.

TR2: Start/Stop control for Timer 2. TR2 = 1 starts the timer.

T2 : Timer or counter select for Timer 2. C/ T2 = 0 for timer function. C/ T2 = 1 for external

event counter (falling edge triggered).

CP/

RL2 : Capture/Reload select. CP/ RL2 = 1 causes captures to occur on negative transitions at

T2EX if EXEN2 = 1. CP/

RL2 = 0 causes automatic reloads to occur when Timer 2

overflows or negative transitions occur at T2EX when EXEN2 = 1. When either RCLK or

TCLK = 1, this bit is ignored and the timer is forced to auto-reload on Timer 2 overflow.

Table 7-1 : Timer 2 Operating Modes

RCLK + TCLK

CP/RL2

TR2

DCEN

Mode

OFF

Baud-Rate Generation

Capture

Auto-Reload Up-only

Auto-Reload Up/Down

7.1

Capture mode

In the capture mode, there are two options selected by bit EXEN2 in T2CON. If EXEN2 = 0, Timer 2 is a 16-bit

timer or counter which upon overflow sets bit TF2 in T2CON. This bit can then be used to generate an interrupt. If

EXEN2 = 1, Timer 2 still does the above, but with the added feature that a 1-to-0 transition at external input T2EX

causes the current value in TH2 and TL2 to be captured into RCAP2H and RCAP2L, respectively. In addition, the

transition at T2EX causes bit EXF2 in T2CON to be set. The EXF2 bit, like TF2, can generate an interrupt.

C/T2=0

C/T2=1

T2 pin

TL2

(8 BITS)

TH2

(8 BITS)

TF2

Fosc/12

TR2

RCAP2L RCAP2H

T2 EX pin

EXEN2

EXF2

Transition

Detector

Timer2 Interrupt

Timier2 in Capture Mode

Fig. 7-1： Timer 2 in capture mode

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