AT83EB5114 Atmel Corporation, AT83EB5114 Datasheet - Page 83

• Manufacturer Part Number: AT83EB5114
• Manufacturer: Atmel Corporation

Specifications of AT83EB5114

• Max. Operating Frequency: 24 MHz
• Cpu: 8051-12C
• Max I/o Pins: 11
• Adc Channels: 6
• Adc Resolution (bits): 10
• Adc Speed (ksps): 50
• Sram (kbytes): 0.25
• Eeprom (bytes): 256
• Operating Voltage (vcc): 3.0 to 3.6
• Timers: 4
• Mask Rom (kbytes): 4
• Watchdog: Yes

Stacked EEPROM
Overview
Protocol
4311C–8051–02/08
The AT8xEB5114 features a stacked 2-wire serial data EEPROM. The data EEPROM
allows to save up to 256 bytes. The EEPROM is internally connected to P3.6 and P3.7
which are respectively connected to the SDA and the SCL pins.
In order to access this memory, it is necessary to use software subroutines according to
the AT24C02 datasheet. Nevertheless, because the internal pull-up resistors of the
AT8xEB5114 is quite high (around 100KΩ), the protocol should be slowed in order to be
sure that the SDA pin can rise to the high level before reading it.
Another solution to keep the access to the EEPROM in specification is to work with a
software pull-up.
Using a software pull-up, consists of forcing a low level at the output pin of the microcon-
troller before configuring it as an input (high level).
The C51 the ports are “quasi-bidirectional” ports. It means that the ports can be config-
ured as output low or as input high. In case a port is configured as an output low, it can
sink a current and all internal pull-ups are disconnected. In case a port is configured as
an input high, it is pulled up with a strong pull-up (a few hundreds Ohms resistor) for 2
clock periods. Then, if the port is externally connected to a low level, it is only kept high
with a weak pull up (around 100KΩ), and if not, the high level is latched high thanks to a
medium pull (around 10kΩ).
Thus, when the port is configured as an input, and when this input has been read at a
low level, there is a pull-up of around 100KΩ, which is quite high, to quickly load the
SDA capacitance. So in order to help the reading of a high level just after the reading of
a low level, it is possible to force a transition of the SDA port from an input state (1), to
an output low state (0), followed by a new transition from this output low state to input
state; In this case, the high pull-up has been replaced with a low pull-up which warran-
ties a good reading of the data.
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