AT89C5131A-L Atmel Corporation, AT89C5131A-L Datasheet - Page 157

• Manufacturer Part Number: AT89C5131A-L
• Manufacturer: Atmel Corporation

Specifications of AT89C5131A-L

• Flash (kbytes): 32 Kbytes
• Max. Operating Frequency: 48 MHz
• Cpu: 8051-12C
• Max I/o Pins: 34
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Sram (kbytes): 1.25
• Eeprom (bytes): 1024
• Self Program Memory: API
• Operating Voltage (vcc): 3.0 to 3.6
• Timers: 4
• Isp: UART/USB
• Watchdog: Yes

ONCE Mode (ON
Chip Emulation)
4338F–USB–08/07
The ONCE mode facilitates testing and debugging of systems using AT89C5131A-L
without removing the circuit from the board. The ONCE mode is invoked by driving cer-
tain pins of the AT89C5131A-L; the following sequence must be exercised:
•
•
While the AT89C5131A-L is in ONCE mode, an emulator or test CPU can be used to
drive the circuit Table 111 shows the status of the port pins during ONCE mode.
Normal operation is restored when normal reset is applied.
Table 111. External Pin Status during ONCE Mode
Pull ALE low while the device is in reset (RST high) and PSEN is high.
Hold ALE low as RST is deactivated.
pull-up
Weak
ALE
PSEN
pull-up
Weak
Port 0
Float
Port 1
pull-up
Weak
Port 2
pull-up
Weak
Port 3
pull-up
Weak
Port I2
Float
XTAL1/2
Active
157