T89C51RD2-SLSIM Atmel, T89C51RD2-SLSIM Datasheet - Page 48

• Manufacturer Part Number: T89C51RD2-SLSIM
• Description: IC MICRO CTRL 64K FLASH 44PLCC
• Manufacturer: Atmel
• Series: 89Cr

Specifications of T89C51RD2-SLSIM

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: SPI, UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 64KB (64K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 1.25K 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
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Data Converters: -

ONCE
Emulation)
48
(TM)
T89C51RD2
Mode (ON Chip
The ONCE mode facilitates testing and debugging of systems using T89C51RD2 with-
out removing the circuit from the board. The ONCE mode is invoked by driving certain
pins of the T89C51RD2; the following sequence must be exercised:
•
•
While the T89C51RD2 is in ONCE mode, an emulator or test CPU can be used to drive
the circuit. Table 30. shows the status of the port pins during ONCE mode.
Normal operation is restored when normal reset is applied.
Table 30. External Pin Status during ONCE Mode
(a) "Once" is a registered trademark of Intel Corporation.
Weak pull-up
Pull ALE low while the device is in reset (RST high) and PSEN is high.
Hold ALE low as RST is deactivated.
ALE
Weak pull-up
PSEN
Port 0
Float
Weak pull-up
Port 1
Weak pull-up
Port 2
Weak pull-up
Port 3
4243G–8051–05/03
XTAL1/2
Active