AT87C51RC2-3CSUM Atmel, AT87C51RC2-3CSUM Datasheet - Page 48

• Manufacturer Part Number: AT87C51RC2-3CSUM
• Description: IC 8051 MCU 32K OTP 40MHZ 40DIP
• Manufacturer: Atmel
• Series: 87Cr

Specifications of AT87C51RC2-3CSUM

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 40/20MHz
• Connectivity: UART/USART
• Peripherals: POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 32KB (32K x 8)
• Program Memory Type: OTP
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 4.5 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-DIP (0.600", 15.24mm)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Data Converters: -

6.9
48
ONCE
AT/TS8xC51Rx2
TM
Mode (ON Chip Emulation)
The ONCE mode facilitates testing and debugging of systems using TS8xC51Rx2 without
removing the circuit from the board. The ONCE mode is invoked by driving certain pins of the
TS80C51Rx2; the following sequence must be exercised:
While the TS80C51Rx2 is in ONCE mode, an emulator or test CPU can be used to drive the cir-
cuit Table 26. shows the status of the port pins during ONCE mode.
Normal operation is restored when normal reset is applied.
Table 6-23.
• Pull ALE low while the device is in reset (RST high) and PSEN is high.
• Hold ALE low as RST is deactivated.
Weak pull-up
ALE
External Pin Status during ONCE Mode
Weak pull-up
PSEN
Port 0
Float
Weak pull-up
Port 1
Weak pull-up
Port 2
Weak pull-up
Port 3
4188F–8051–01/08
XTAL1/2
Active