IS80C52 Datasheet, PDF (16/48 Pages) Integrated Silicon Solution, Inc – CMOS SINGLE CHIP LOW VOLTAGE 8-BIT MICROCONTROLLER

IS80C52
IS80C32
ISSI ^®
Mode 1:
Mode 1 is the same as Mode 0, except that the Timer
register is run with all 16 bits. The clock is applied to the
combined high and low timer registers (TL1/TH1). As
clock pulses are received, the timer counts up: 0000H,
0001H, 0002H, etc. An overflow occurs on the FFFFH-to-
0000H overflow flag. The timer continues to count. The
overflow flag is the TF1 bit in TCON that is read or written
by software (see Figure 9).
Mode 2:
Mode 2 configures the Timer register as an 8-bit Counter
(TL1) with automatic reload, as shown in Figure 10.
Overflow from TL1 not only sets TF1, but also reloads TL1
with the contents of TH1, which is preset by software. The
reload leaves the TH1 unchanged. Mode 2 operation is
the same for Timer/Counter 0.
Mode 3:
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 10. TL0 uses the
Timer 0 control bits: C/T, GATE, TR0, INT0, and TF0. TH0
is locked into a timer function (counting machine cycles)
and over the use of TR1 and TF1 from Timer 1. Thus, TH0
now controls the Timer 1 interrupt.
Mode 3 is for applications requiring an extra 8-bit timer or
counter. With Timer 0 in Mode 3, the IS80C51/31 can
appear to have three Timer/Counters, and an IS80C52/32
can appear to have four. When Timer 0 is in Mode 3, Timer
1 can be turned on and off by switching it out of and into
its own Mode 3. In this case, Timer 1 can still be used by
the serial port as a baud rate generator or in any application
not requiring an interrupt.
OSC
DIVIDE 12
T1 PIN
GATE
INT0 PIN
C/T = 0
C/T = 1
TR1
TL1
(8 BITS)
CONTROL
TF1
RELOAD
TH1
(8 BITS)
Figure 10. Timer/Counter 1 Mode 2: 8-Bit Auto-Reload
INTERRUPT
OSC
DIVIDE 12
1/12F OSC
1/12F OSC
T0 PIN
GATE
C/T = 0
C/T = 1
TR0
TL0
(8 BITS)
CONTROL
TF0
INTERRUPT
INT0 PIN
1/12F OSC
TR1
TH0
(8 BITS)
CONTROL
TF1
INTERRUPT
Figure 11. Timer/Counter 0 Mode 3: Two 8-Bit Counters
16
Integrated Silicon Solution, Inc. — 1-800-379-4774
MC004-1D
11/19/98