Specifications

53
3706C–MICRO–2/11
AT89LP3240/6440
Figure 11-2. Timer/Counter 1 Mode 1: 16-bit Auto-Reload
11.3 Mode 2 – 8-bit Auto-Reload Timer/Counter
Mode 2 configures the Timer register as an 8-bit Counter (TL1) with automatic reload, as shown
in Figure 11-3. Overflow from TL1 not only sets TF1, but also reloads TL1 with the contents of
TH1, which is preset by software. The reload leaves TH1 unchanged. Mode 2 operation is the
same for Timer/Counter 0.
Figure 11-3. Timer/Counter 1 Mode 2: 8-bit Auto-Reload
Note: RH1/RL1 are not required by Timer 1 during Mode 2 and may be used as temporary storage
registers.
11.4 Mode 3 – 8-bit Split Timer
Timer 1 in Mode 3 simply holds its count. The effect is the same as setting TR1 = 0. Timer 0 in
Mode 3 establishes TL0 and TH0 as two separate counters. The logic for Mode 3 on Timer 0 is
shown in Figure 11-4. TL0 uses the Timer 0 control bits: C/T, GATE0, TR0, INT0
, and TF0. TH0
is locked into a timer function (counting clock cycles) and takes over the use of TR1 and TF1
from Timer 1. Thus, TH0 now controls the Timer 1 interrupt. While Timer 0 is in Mode 3, Timer 1
will still obey its settings in TMOD but cannot generate an interrupt.
OSC
T1 Pin
TR1
GATE1
INT1 Pin
TL1
(8 Bits)
Control
Interrupt
C/T = 0
C/T =1
TH1
(8 Bits)
TF1
RL1
(8 Bits)
RH1
(8 Bits)
Reload
÷TPS
Mode 2: Time-out Period
256 TH0–()
Oscillator Frequency
-------------------------------------------------------
TPS 1+()×=
OSC
T1 Pin
TR1
GATE1
TF1
TL1
(8 Bits)
TH1
(8 Bits)
Control
Reload
Interrupt
INT0 Pin
C/T = 0
C/T = 1
÷TPS