AT87C52X2-3CSUM【PDF 4/55 页】IC 8051 MCU 8K OTP 40MHZ 40DIP

TS8xCx2X2

4184I–8051–02/08

Timer 2

The timer 2 in the

TS80C52X2 is compatible with the timer 2 in the 80C52.

It is a 16-bit timer/counter: the count is maintained by two eight-bit timer registers, TH2

and TL2, connected in cascade. It is controlled by T2CON register (See Table 5) and

T2MOD register (See Table 6). Timer 2 operation is similar to Timer 0 and Timer 1. C/T2

selects FOSC/12 (timer operation) or external pin T2 (counter operation) as the timer

clock input. Setting TR2 allows TL2 to be incremented by the selected input.

Timer 2 has 3 operating modes: capture, autoreload and Baud Rate Generator. These

modes are selected by the combination of RCLK, TCLK and CP/RL2 (T2CON), as

described in the Atmel 8-bit Microcontroller Hardware description.

Refer to the Atmel 8-bit Microcontroller Hardware description for the description of Cap-

ture and Baud Rate Generator Modes.

TS80C52X2 Timer 2 includes the following enhancements:

Auto-reload mode with up or down counter

Programmable clock-output

Auto-reload Mode

The Auto-reload mode configures timer 2 as a 16-bit timer or event counter with auto-

matic reload. If DCEN bit in T2MOD is cleared, timer 2 behaves as in 80C52 (refer to the

Atmel 8-bit Microcontroller Hardware description). If DCEN bit is set, timer 2 acts as an

Up/down timer/counter as shown in Figure 4. In this mode the T2EX pin controls the

direction of count.

When T2EX is high, timer 2 counts up. Timer overflow occurs at FFFFh which sets the

TF2 flag and generates an interrupt request. The overflow also causes the 16-bit value

in RCAP2H and RCAP2L registers to be loaded into the timer registers TH2 and TL2.

When T2EX is low, timer 2 counts down. Timer underflow occurs when the count in the

timer registers TH2 and TL2 equals the value stored in RCAP2H and RCAP2L registers.

The underflow sets TF2 flag and reloads FFFFh into the timer registers.

The EXF2 bit toggles when timer 2 overflows or underflows according to the the direc-

tion of the count. EXF2 does not generate any interrupt. This bit can be used to provide

17-bit resolution.

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