AT89C55WD-24JU Atmel, AT89C55WD-24JU Datasheet - Page 11
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AT89C55WD-24JU
Manufacturer Part Number
AT89C55WD-24JU
Description
IC 8051 MCU FLASH 20K 44PLCC
Manufacturer
Atmel
Series
89Cr
Datasheet
1.AT89C55WD-24AU.pdf
(35 pages)
Specifications of AT89C55WD-24JU
Core Processor
8051
Core Size
8-Bit
Speed
24MHz
Connectivity
UART/USART
Peripherals
WDT
Number Of I /o
32
Program Memory Size
20KB (20K x 8)
Program Memory Type
FLASH
Ram Size
256 x 8
Voltage - Supply (vcc/vdd)
4.5 V ~ 5.5 V
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
44-PLCC
Cpu Family
89C
Device Core
8051
Device Core Size
8b
Frequency (max)
24MHz
Total Internal Ram Size
256Byte
# I/os (max)
32
Number Of Timers - General Purpose
3
Operating Supply Voltage (typ)
5V
Operating Supply Voltage (max)
5.5V
Operating Supply Voltage (min)
4V
Instruction Set Architecture
CISC
Operating Temp Range
-40C to 85C
Operating Temperature Classification
Industrial
Mounting
Surface Mount
Pin Count
44
Package Type
PLCC
Processor Series
AT89x
Core
8051
Data Bus Width
8 bit
Data Ram Size
256 B
Interface Type
UART
Maximum Clock Frequency
24 MHz
Number Of Programmable I/os
32
Number Of Timers
3
Operating Supply Voltage
4 V to 6 V
Maximum Operating Temperature
+ 85 C
Mounting Style
SMD/SMT
3rd Party Development Tools
PK51, CA51, A51, ULINK2
Minimum Operating Temperature
- 40 C
No. Of I/o's
32
Ram Memory Size
256Byte
Cpu Speed
24MHz
No. Of Timers
3
Digital Ic Case Style
LCC
Supply Voltage Range
4V To 5.5V
Rohs Compliant
Yes
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Eeprom Size
-
Data Converters
-
Lead Free Status / Rohs Status
Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
AT89C55WD-24JU
Manufacturer:
ATM
Quantity:
1 980
Company:
Part Number:
AT89C55WD-24JU
Manufacturer:
ATMEL
Quantity:
42 279
Company:
Part Number:
AT89C55WD-24JU
Manufacturer:
ATM
Quantity:
1 980
Part Number:
AT89C55WD-24JU
Manufacturer:
ATMEL/爱特梅尔
Quantity:
20 000
12. Timer 2
12.1
12.2
1921D–MICRO–6/08
Capture Mode
Auto-reload (Up or Down Counter)
Timer 2 is a 16-bit Timer/Counter that can operate as either a timer or an event counter. The
type of operation is selected by bit C/T2 in the SFR T2CON (shown in
three operating modes: capture, auto-reload (up or down counting), and baud rate generator.
The modes are selected by bits in T2CON, as shown in
Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the TL2 register is
incremented every machine cycle. Since a machine cycle consists of 12 oscillator periods, the
count rate is 1/12 of the oscillator frequency.
Table 12-1.
In the Counter function, the register is incremented in response to a 1-to-0 transition at its corre-
sponding external input pin, T2. In this function, the external input is sampled during S5P2 of
every machine cycle. When the samples show a high in one cycle and a low in the next cycle,
the count is incremented. The new count value appears in the register during S3P1 of the cycle
following the one in which the transition was detected. Since two machine cycles (24 oscillator
periods) are required to recognize a 1-to-0 transition, the maximum count rate is 1/24 of the
oscillator frequency. To ensure that a given level is sampled at least once before it changes, the
level should be held for at least one full machine cycle.
In the capture mode, two options are selected by bit EXEN2 in T2CON. If EXEN2 = 0, Timer 2 is
a 16-bit timer or counter which upon overflow sets bit TF2 in T2CON. This bit can then be used
to generate an interrupt. If EXEN2 = 1, Timer 2 performs the same operation, but a 1-to-0 transi-
tion at external input T2EX also causes the current value in TH2 and TL2 to be captured into
RCAP2H and RCAP2L, respectively. In addition, the transition at T2EX causes bit EXF2 in
T2CON to be set. The EXF2 bit, like TF2, can generate an interrupt. The capture mode is illus-
trated in
Timer 2 can be programmed to count up or down when configured in its 16-bit auto-reload
mode. This feature is invoked by the DCEN (Down Counter Enable) bit located in the
SFR T2MOD (see
count up. When DCEN is set, Timer 2 can count up or down, depending on the value of the
T2EX pin.
RCLK +TCLK
Figure
0
0
1
X
Timer 2 Operating Modes
12-1.
Table
12-2). Upon reset, the DCEN bit is set to 0 so that timer 2 will default to
CP/RL2
X
X
0
1
TR2
1
1
1
0
Table
MODE
16-bit Auto-Reload
16-bit Capture
Baud Rate Generator
(Off)
5-2.
AT89C55WD
Table
5-2). Timer 2 has
11