P89LV51RD2 Philips Semiconductors, P89LV51RD2 Datasheet - Page 34

• Manufacturer Part Number: P89LV51RD2
• Description: 8-bit 80C51 3 V low power 64 kB Flash microcontroller with 1 kB RAM
• Manufacturer: Philips Semiconductors

Philips Semiconductors
9397 750 14101
Product data
Fig 13. Timer 2 in auto-reload mode (DCEN = 0)
OSC
T2 pin
T2EX pin
¸
6
transition
detector
In this mode, there are two options selected by bit EXEN2 in T2CON register. If
EXEN2 = 0, then Timer 2 counts up to 0FFFFH and sets the TF2 (Overflow Flag) bit
upon overflow. This causes the Timer 2 registers to be reloaded with the 16-bit value
in RCAP2L and RCAP2H. The values in RCAP2L and RCAP2H are preset by
software means.
Auto reload frequency when Timer 2 is counting up can be determined from this
formula:
Where SupplyFrequency is either f
(C/T2 =
If EXEN2 =
transition at input T2EX. This transition also sets the EXF2 bit. The Timer 2 interrupt,
if enabled, can be generated when either TF2 or EXF2 is
Microcontroller’s hardware will need three consecutive machine cycles in order to
recognize falling edge on T2EX and set EXF2 =
has to be sampled as ‘1’; in the second machine cycle it has to be sampled as ‘0’, and
in the third machine cycle EXF2 will be set to
In
allows pin T2EX to control the direction of count. When a logic ‘1’ is applied at pin
T2EX Timer 2 will count up. Timer 2 will overflow at 0FFFFH and set the TF2 flag,
which can then generate an interrupt, if the interrupt is enabled. This timer overflow
also causes the 16-bit value in RCAP2L and RCAP2H to be reloaded into the timer
registers TL2 and TH2.
------------------------------------------------------------------------------- -
65536
Figure
C/T2 = 0
C/T2 = 1
SupplyFrequency
1
).
14, DCEN =
RCAP2H RCAP2L
EXEN2
1
, a 16-bit reload can be triggered either by an overflow or by a 1-to-0
control
Rev. 03 — 11 October 2004
TR2
control
1
reload
and Timer 2 is enabled to count up or down. This mode
RCAP2L RCAP2H
(8-bits)
TL2
osc
(C/T2 = 0) or frequency of signal on T2 pin
(8-bits)
TH2
8-bit microcontrollers with 80C51 core
‘1’
.
1
: in the first machine cycle pin T2EX
EXF2
TF2
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
‘1’
P89LV51RD2
002aaa524
.
interrupt
Timer 2
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