Hardware manual

Common Features Description

Atmel 8051 Microcontrollers Hardware Manual 2-35

4316A–8051–01/04

Figure 2-13. Timer/Counter 1 Mode 0: 13-bit Counter

2.11.2 Mode 1 (16-bit

Timer)

Mode 1 configures Timer 1 as a 16-bit timer with the TH1 and TL1 registers connected

in cascade (see Figure 2-10). The selected input increments the TL1 register.

2.11.3 Mode 2 (8-bit Timer

with Auto Reload)

Mode 2 configures Timer 1 as an 8-bit timer (TL1 register) with automatic reload from

the TH1 register on overflow (see Figure 2-11). TL1 overflow sets the TF1 flag in the

TCON register and reloads TL1 with the contents of TH1, which is preset by software.

The reload leaves TH1 unchanged.

Figure 2-14. Timer/Counter 1 Mode 2: 8-bit Auto-reload

2.11.4 Mode 3 (Halt) Placing Timer 1 in mode 3 causes it to halt and hold its count. This can be used to halt

Timer 1 when TR1 run control bit is not available i.e., when Timer 0 is in mode 3.

2.11.5 Interrupt Each timer handles one interrupt source; that is the timer overflow flag TF0 or TF1. This

flag is set every time an overflow occurs. Flags are cleared when vectoring to the timer

interrupt routine. Interrupts are enabled by setting

ETx bit in IE0 register. This assumes

interrupts are globally enabled by setting EA bit in the IE0 register.

Periph

Clock

INT1 Pin

Periph

Clock