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OCPRF100 MP Server System Technical Product Specification
Revision 1.0
96
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 I
2
C serial port.
8.3.2.4 I
2
C Serial Communication-SI01
The I
2
C 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.
8.3.2.5 I
2
C Electrical Input/Output Specifications
The I
2
C 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 lev-
els have been defined:
V
ILmax
= 1.5 V (maximum input low voltage).
V
IHmin
= 3 V (minimum input high voltage).
Devices operating on a fixed supply voltage different from +5 V (e.g., I
2
L), must also have these
input levels of 1.5 V and 3 V for V
IL
and V
IH
respectively.
For devices operating over a wide range of supply voltages (e.g., CMOS), the following levels
have been defined:
V
ILmax
= 0.3 V
DD
(maximum input low voltage).
V
IHmin
= 0.7 V
DD
(minimum input high voltage).
For both groups of devices, the maximum output low value has been defined as follows:
V
OLmax
= 0.4 V (maximum output voltage low) at 3 mA sink current.
The maximum low-level input current at V
OLmax
of both the SDA pin and the SCL pin of an I
2
C
device is -10µA, including the leakage current of a possible output stage.
The maximum high-level input current at 0.9V
DD
of both the SDA pin and SCL pin of an I
2
C
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 I
2
C device is 10 pf.
8.3.2.6 Noise Margin
Noise margin minimum on the low level is 0.1 V
DD
.