p89lpc972fn NXP Semiconductors, p89lpc972fn Datasheet - Page 30

• Manufacturer Part Number: p89lpc972fn
• Description: 8-bit Microcontroller With Accelerated Two-clock 80c51 Core 2kb/4 Kb/8 Kb Wide-voltage Byte-erasable ?ash
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89LPC97X_1
Preliminary data sheet
7.19.3.1 Mode 3
7.19.3.2 Mode 6
7.19.1 Mode 0
7.19.2 Mode 1
7.19.3 Mode 2
7.19.4 Timer overflow toggle output
7.20 Timers/counters 2, 3 and 4
In the ‘Counter’ function, the register is incremented in response to a 1-to-0 transition at its
corresponding count input pin, T0 or T1. In this function, the count input is sampled once
during every machine cycle.
Timer 0 and Timer 1 have five operating modes (Modes 0, 1, 2, 3 and 6). Modes 0, 1, 2
and 6 are the same for both Timers/Counters. Mode 3 is different.
Putting either Timer into Mode 0 makes it look like an 8048 Timer, which is an 8-bit
Counter with a divide-by-32 prescaler. In this mode, the Timer register is configured as a
13-bit register. Mode 0 operation is the same for Timer 0 and Timer 1.
Mode 1 is the same as Mode 0, except that all 16 bits of the timer register are used.
Mode 2 configures the Timer register as an 8-bit Counter with automatic reload. Mode 2
operation is the same for Timer 0 and Timer 1.
When Timer 1 is in Mode 3 it is stopped. Timer 0 in Mode 3 forms two separate 8-bit
counters and is provided for applications that require an extra 8-bit timer. When Timer 1 is
in Mode 3 it can still be used by the serial port as a baud rate generator.
In this mode, the corresponding timer can be changed to a PWM with a full period of
256 timer clocks.
Timers 0 and 1 can be configured to automatically toggle a port output whenever a timer
overflow occurs. The same device pins that are used for the T0 and T1 count inputs are
also used for the timer toggle outputs. The port outputs will be a logic 1 prior to the first
timer overflow when this mode is turned on.
The P89LPC970/971/972 has three external 16-bit timer/counters. All can be configured
to operate either as timers or event counters. An option to automatically toggle pin Tx (x =
2, 3 or 4) upon timer overflow has been added.
In the ‘Timer’ function, the register is incremented every PCLK.
In the ‘Counter’ function, the register is incremented in response to a 1-to-0 transition at its
corresponding count input pin (T2/T3 /T4). In this function, the count input is sampled
once during every machine cycle.
Only external Timer 2/3/4 has the external input pin TxEX (x = 2, 3 or 4). A 1-to-0
transition on this pin can trigger a reload or capture event.
Timer 2, Timer 3 and Timer 4 have three operating modes (Modes 0, 1 and 2).
Rev. 01 — 17 December 2009
8-bit microcontroller with accelerated two-clock 80C51 core
P89LPC970/971/972
© NXP B.V. 2009. All rights reserved.
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