80C51 8-bit microcontroller family 8KB/16KB/32KB/64K" />
參數(shù)資料
型號(hào)： P87C51RD2FBD/01,15
廠商： NXP Semiconductors
文件頁(yè)數(shù)： 5/67頁(yè)
文件大小： 0K
描述： IC 80C51 MCU 8BIT 44LQFP
標(biāo)準(zhǔn)包裝： 800
系列： 87C
核心處理器： 8051
芯體尺寸： 8-位
速度： 33MHz
連通性： EBI/EMI，UART/USART
外圍設(shè)備： POR，PWM，WDT
輸入/輸出數(shù)： 32
程序存儲(chǔ)器容量： 64KB（64K x 8）
程序存儲(chǔ)器類型： OTP
RAM 容量： 1K x 8
電壓 - 電源 (Vcc/Vdd)： 2.7 V ~ 5.5 V
振蕩器型： 內(nèi)部
工作溫度： -40°C ~ 85°C
封裝/外殼： 44-LQFP
包裝： 托盤
其它名稱： 568-7909
P87C51RD2FBD/01,15-ND
Philips Semiconductors
Product data
P87C51RA2/RB2/RC2/RD2
80C51 8-bit microcontroller family 8KB/16KB/32KB/64KB OTP
with 512B/1KB RAM, low voltage (2.7 to 5.5 V), low power, high
speed (30/33 MHz)
2003 Jan 24
13
TIMER 0 AND TIMER 1 OPERATION
Timer 0 and Timer 1
The “Timer” or “Counter” function is selected by control bits C/T in
the Special Function Register TMOD. These two Timer/Counters
have four operating modes, which are selected by bit-pairs (M1, M0)
in TMOD. Modes 0, 1, and 2 are the same for both Timers/Counters.
Mode 3 is different. The four operating modes are described in the
following text.
Mode 0
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. Figure 3
shows the Mode 0 operation.
In this mode, the Timer register is configured as a 13-bit register. As
the count rolls over from all 1s to all 0s, it sets the Timer interrupt
flag TFn. The counted input is enabled to the Timer when TRn = 1
and either GATE = 0 or INTn = 1. (Setting GATE = 1 allows the
Timer to be controlled by external input INTn, to facilitate pulse width
measurements). TRn is a control bit in the Special Function Register
TCON (Figure 4).
The 13-bit register consists of all 8 bits of THn and the lower 5 bits
of TLn. The upper 3 bits of TLn are indeterminate and should be
ignored. Setting the run flag (TRn) does not clear the registers.
Mode 0 operation is the same for Timer 0 as for Timer 1. There are
two different GATE bits, one for Timer 1 (TMOD.7) and one for Timer
0 (TMOD.3).
Mode 1
Mode 1 is the same as Mode 0, except that the Timer register is
being run with all 16 bits.
Mode 2
Mode 2 configures the Timer register as an 8-bit Counter (TLn) with
automatic reload, as shown in Figure 5. Overflow from TLn not only
sets TFn, but also reloads TLn with the contents of THn, which is
preset by software. The reload leaves THn unchanged.
Mode 2 operation is the same for Timer 0 as for Timer 1.
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 6. TL0
uses the Timer 0 control bits: C/T, GATE, TR0, and TF0 as well as
pin INT0. TH0 is locked into a timer function (counting machine
cycles) and takes over the use of TR1 and TF1 from Timer 1. Thus,
TH0 now controls the “Timer 1” interrupt.
Mode 3 is provided for applications requiring an extra 8-bit timer on
the counter. With Timer 0 in Mode 3, an 80C51 can look like it has
three Timer/Counters. 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, or
can still be used by the serial port as a baud rate generator, or in
fact, in any application not requiring an interrupt.
GATE
C/T
M1
M0
GATE
C/T
M1
M0
BIT
SYMBOL
FUNCTION
TMOD.3/
GATE
Gating control when set. Timer/Counter “n” is enabled only while “INTn” pin is high and
TMOD.7
“TRn” control pin is set. when cleared Timer “n” is enabled whenever “TRn” control bit is set.
TMOD.2/
C/T
Timer or Counter Selector cleared for Timer operation (input from internal system clock.)
TMOD.6
Set for Counter operation (input from “Tn” input pin).
M1
M0
OPERATING
0
8048 Timer: “TLn” serves as 5-bit prescaler.
0
1
16-bit Timer/Counter: “THn” and “TLn” are cascaded; there is no prescaler.
1
0
8-bit auto-reload Timer/Counter: “THn” holds a value which is to be reloaded
into “TLn” each time it overflows.
1
(Timer 0) TL0 is an 8-bit Timer/Counter controlled by the standard Timer 0 control bits.
TH0 is an 8-bit timer only controlled by Timer 1 control bits.
1
(Timer 1) Timer/Counter 1 stopped.
SU01580
TIMER 1
TIMER 0
Not Bit Addressable
TMOD
Address = 89H
Reset Value = 00H
76
543
2
1
0
Figure 2. Timer/Counter 0/1 Mode Control (TMOD) Register
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