C8051F340/1/2/3/4/5/6/7

21.1.4. Mode 3: Two 8-bit Counter/Timers (Timer 0 Only)

In Mode 3, Timer 0 is configured as two separate 8-bit counter/timers held in TL0 and TH0. The counter/ timer in TL0 is controlled using the Timer 0 control/status bits in TCON and TMOD: TR0, C/T0, GATE0 and TF0. TL0 can use either the system clock or an external input signal as its timebase. The TH0 register is restricted to a timer function sourced by the system clock or prescaled clock. TH0 is enabled using the Timer 1 run control bit TR1. TH0 sets the Timer 1 overflow flag TF1 on overflow and thus controls the Timer 1 interrupt.

Timer 1 is inactive in Mode 3. When Timer 0 is operating in Mode 3, Timer 1 can be operated in Modes 0, 1 or 2, but cannot be clocked by external signals nor set the TF1 flag and generate an interrupt. However, the Timer 1 overflow can be used to generate baud rates for the SMBus and/or UART, and/or initiate ADC conversions. While Timer 0 is operating in Mode 3, Timer 1 run control is handled through its mode set- tings. To run Timer 1 while Timer 0 is in Mode 3, set the Timer 1 Mode as 0, 1, or 2. To disable Timer 1, configure it for Mode 3.

 

 

 

CKCON

 

T

T

T

T

T

T

S

S

 

3

3

2

2

1

0

C

C

 

M

M

M

M

M

M

A

A

 

H

L

H

L

 

 

 

1

0

TMOD

G C T T G C T T A / 1 1 A / 0 0

TT M M T T M M E 1 1 0 E 0 1 0

1 0

Pre-scaled Clock

0

 

TR1

SYSCLK

1

 

0

 

1

T0

TR0

CrossbarGATE0

TH0

(8 bits)

TL0

(8 bits)

 

TF1

Interrupt

 

TR1

 

 

TF0

Interrupt

TCON

TR0

 

IE1

 

IT1

 

IE0

 

 

IT0

 

/INT0

IN0PL

XOR

Figure 21.3. T0 Mode 3 Block Diagram

246

Rev. 0.5

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Image 246
Silicon Laboratories C8051F345, C8051F347, C8051F346 T0 Mode 3 Block Diagram, Mode 3 Two 8-bit Counter/Timers Timer 0 Only