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

21.1.3. Mode 2: 8-bit Counter/Timer with Auto-Reload

Mode 2 configures Timer 0 and Timer 1 to operate as 8-bit counter/timers with automatic reload of the start value. TL0 holds the count and TH0 holds the reload value. When the counter in TL0 overflows from all ones to 0x00, the timer overflow flag TF0 (TCON.5) is set and the counter in TL0 is reloaded from TH0. If Timer 0 interrupts are enabled, an interrupt will occur when the TF0 flag is set. The reload value in TH0 is not changed. TL0 must be initialized to the desired value before enabling the timer for the first count to be correct. When in Mode 2, Timer 1 operates identically to Timer 0.

Both counter/timers are enabled and configured in Mode 2 in the same manner as Mode 0. Setting the TR0 bit (TCON.4) enables the timer when either GATE0 (TMOD.3) is logic 0 or when the input signal /INT0 is active as defined by bit IN0PL in register INT01CF (see Section “9.3.2. External Interrupts” on page 87 for details on the external input signals /INT0 and /INT1).

 

 

 

 

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

INT01CF

I

I

I

I

I

I

I

I

N

N

N

N

N

N

N

N

1

1

1

1

0

0

0

0

P

S

S

S

P

S

S

S

L

L

L

L

L

L

L

L

 

2

1

0

 

2

1

0

 

 

 

 

 

 

 

 

Pre-scaled Clock

 

0

 

 

 

 

0

SYSCLK 1

T0

Crossbar

1

TR0

GATE0

TCLK

TL0

(8 bits)

TH0

(8 bits)

Reload

 

TF1

 

 

TR1

 

 

TF0

Interrupt

 

TR0

 

TCON

IE1

 

IT1

 

IE0

 

IT0

 

 

 

IN0PL XOR /INT0

Figure 21.2. T0 Mode 2 Block Diagram

Rev. 0.5

245

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Image 245
Silicon Laboratories C8051F344, C8051F347, C8051F346 T0 Mode 2 Block Diagram, Mode 2 8-bit Counter/Timer with Auto-Reload