AT89C51RE2 Atmel Corporation, AT89C51RE2 Datasheet - Page 82

• Manufacturer Part Number: AT89C51RE2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RE2

• Flash (kbytes): 128 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 34
• Spi: 1
• Uart: 2
• Sram (kbytes): 8.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART/OCD
• Watchdog: Yes

Programmable
Counter Array
PCA
82
AT89C51RE2
The PCA provides more timing capabilities with less CPU intervention than the standard
timer/counters. Its advantages include reduced software overhead and improved accuracy. The
PCA consists of a dedicated timer/counter which serves as the time base for an array of five
compare/capture modules. Its clock input can be programmed to count any one of the following
signals:
•
•
•
•
Each compare/capture modules can be programmed in any one of the following modes:
•
•
•
•
Module 4 can also be programmed as a watchdog timer (See Section "PCA Watchdog Timer",
page 93).
When the compare/capture modules are programmed in the capture mode, software timer, or
high speed output mode, an interrupt can be generated when the module executes its function.
All five modules plus the PCA timer overflow share one interrupt vector.
The PCA timer/counter and compare/capture modules share Port 1 for external I/O. These pins
are listed below. If the port is not used for the PCA, it can still be used for standard I/O.
The PCA timer is a common time base for all five modules (See Figure 30). The timer count
source is determined from the CPS1 and CPS0 bits in the CMOD register (Table 54) and can be
programmed to run at:
•
•
•
•
Peripheral clock frequency (F
Peripheral clock frequency (F
Timer 0 overflow
External input on ECI (P1.2)
Rising and/or falling edge capture
Software timer
High-speed output
Pulse width modulator
1/6 the
1/2 the
The Timer 0 overflow
The input on the ECI pin (P1.2)
peripheral clock frequency (F
peripheral clock frequency (F
PCA component
16-bit Module 0
16-bit Module 1
16-bit Module 2
16-bit Module 3
16-bit Counter
CLK PERIPH
CLK PERIPH
)
)
CLK PERIPH
CLK PERIPH
÷
÷
2
6
)
)
External I/O Pin
P1.3 / CEX0
P1.4 / CEX1
P1.5 / CEX2
P1.6 / CEX3
P1.2 / ECI
7663E–8051–10/08