OCPRF100 MP Server System Technical Product Specification

Revision 1.0

Since the standard 80C51 onchip functions are the same on the 80C652, the SFR locations, bit locations, and operation are unchanged. The only exception is in the interrupt enable and inter-

rupt priority SFRs. These have been changed to include the interrupt from the I2C serial port.

8.3.2.4I2C Serial Communication-SI01

The I2C pins are alternate functions to port pins P1.6 and P1.7. Because of this, P1.6 and P1.7 on these parts do not have a pull-up structure as found on the 80C51. Therefore P1.6 and P1.7 have open drain outputs on the 80C652.

8.3.2.5I2C Electrical Input/Output Specifications

The I2C bus allows communication between devices made in different technologies, which might also use different supply voltages.

For devices with fixed input levels, operating on a supply voltage of +5 V ± 10%, the following levels have been defined:

VILmax = 1.5 V (maximum input low voltage).

VIHmin = 3 V (minimum input high voltage).

Devices operating on a fixed supply voltage different from +5 V (e.g., I2L), must also have these input levels of 1.5 V and 3 V for VIL and VIH respectively.

For devices operating over a wide range of supply voltages (e.g., CMOS), the following levels have been defined:

VILmax = 0.3 VDD (maximum input low voltage).

VIHmin = 0.7 VDD (minimum input high voltage).

For both groups of devices, the maximum output low value has been defined as follows:

VOLmax = 0.4 V (maximum output voltage low) at 3 mA sink current.

The maximum low-level input current at VOLmax of both the SDA pin and the SCL pin of an I2C device is -10µA, including the leakage current of a possible output stage.

The maximum high-level input current at 0.9VDD of both the SDA pin and SCL pin of an I2C device is 10µA, including the leakage current of a possible output stage.

The maximum capacitance of both the SDA pin and the SCL pin of an I2C device is 10 pf.

8.3.2.6Noise Margin

Noise margin minimum on the low level is 0.1 VDD.

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