AT89C51RD2 Atmel Corporation, AT89C51RD2 Datasheet - Page 73

• Manufacturer Part Number: AT89C51RD2
• Manufacturer: Atmel Corporation

Specifications of AT89C51RD2

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Sram (kbytes): 2
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART
• Watchdog: Yes

17.1
17.2
4235K–8051–05/08
Registers
Interrupt Sources and Vector Addresses
The PCA interrupt vector is located at address 0033H, the SPI interrupt vector is located at
address 004BH and Keyboard interrupt vector is located at address 003BH. All other vectors
addresses are the same as standard C52 devices.
Table 17-1.
A low-priority interrupt can be interrupted by a high priority interrupt, but not by another low-prior-
ity interrupt. A high-priority interrupt can’t be interrupted by any other interrupt source.
If two interrupt requests of different priority levels are received simultaneously, the request of
higher priority level is serviced. If interrupt requests of the same priority level are received simul-
taneously, an internal polling sequence determines which request is serviced. Thus within each
priority level there is a second priority structure determined by the polling sequence.
Table 17-2.
Number
10
0
1
2
3
4
5
6
7
8
9
IPH.x
Priority Level Bit Values
Interrupt Sources and Vector Addresses
0
0
1
1
Polling Priority
10
0
1
2
3
4
6
7
5
8
9
Interrupt Source
Keyboard
Timer 0
Timer 1
Timer 2
Reset
UART
INT0
INT1
PCA
SPI
-
IPL.x
0
1
0
1
CF + CCFn (n = 0 - 4)
TF2+EXF2
Interrupt
Request
KBDIT
RI+TI
SPIIT
TF0
AT89C51RD2/ED2
IE0
IE1
IF1
-
Interrupt Level Priority
3 (Highest)
0 (Lowest)
1
2
Address
Vector
000Bh
001Bh
002Bh
003Bh
004Bh
0000h
0003h
0013h
0023h
0033h
0043h
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