參數(shù)資料
型號: AT89C51ED2-SMSUM
廠商: Atmel
文件頁數(shù): 62/137頁
文件大?。?/td> 0K
描述: IC 8051 MCU FLASH 64K 68PLCC
產(chǎn)品培訓(xùn)模塊: MCU Product Line Introduction
標準包裝: 304
系列: 89C
核心處理器: 8051
芯體尺寸: 8-位
速度: 60MHz
連通性: SPI,UART/USART
外圍設(shè)備: POR,PWM,WDT
輸入/輸出數(shù): 50
程序存儲器容量: 64KB(64K x 8)
程序存儲器類型: 閃存
EEPROM 大?。?/td> 2K x 8
RAM 容量: 2K x 8
電壓 - 電源 (Vcc/Vdd): 2.7 V ~ 5.5 V
振蕩器型: 外部
工作溫度: -40°C ~ 85°C
封裝/外殼: 68-PLCC
包裝: 管件
配用: AT89OCD-01-ND - USB EMULATOR FOR AT8XC51 MCU
30
4235K–8051–05/08
AT89C51RD2/ED2
12. Timer 2
The Timer 2 in the AT89C51RD2/ED2 is the standard C52 Timer 2. It is a 16-bit timer/counter:
the count is maintained by two eight-bit timer registers, TH2 and TL2 are cascaded. It is con-
trolled by T2CON (Table 12-1) and T2MOD (Table 12-2) registers. Timer 2 operation is similar to
Timer 0 and Timer 1. C/T2 selects FOSC/12 (timer operation) or external pin T2 (counter opera-
tion) as the timer clock input. Setting TR2 allows TL2 to increment 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).
Refer to the Atmel 8-bit Microcontroller Hardware Manual for the description of Capture and
Baud Rate Generator Modes.
Timer 2 includes the following enhancements:
Auto-reload mode with up or down counter
Programmable clock-output
12.1
Auto-reload Mode
The auto-reload mode configures Timer 2 as a 16-bit timer or event counter with automatic
reload. If DCEN bit in T2MOD is cleared, Timer 2 behaves as in 80C52 (refer to the Atmel C51
Microcontroller Hardware Manual). If DCEN bit is set, Timer 2 acts as an Up/down timer/counter
as shown in Figure 12-1. 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 under-
flow sets TF2 flag and reloads FFFFh into the timer registers.
The EXF2 bit toggles when Timer 2 overflows or underflows according to the direction of the
count. EXF2 does not generate any interrupt. This bit can be used to provide 17-bit resolution.
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