Hello Everyone,

I would like to check the correctness and also clarify on the details i have mentioned here regarding the port pins of AT89S52 for effective programming.

Initially all ports of AT89S52 are high.

1)a
VOL = Output Low Voltage (Ports 1,2,3) = 0.45 V at each pin
At this condition, sink current (IOL) = 1.6 mA at each pin

port pin in this mode is used to switch 'ON' a PNP Tr
example code: clr p1.x

1)b
VOL1 = Output Low Voltage(1) (Port 0, ALE, PSEN) = .45 V at each pin
At this condition Sink current (IOL) = 3.2 mA at each pin

port pin in this mode is used to switch 'ON' a PNP Tr
example code: clr p1.x

2)a
VOH = Output High Voltage (Ports 1,2,3, ALE, PSEN) at different source current ratings:
source current (IOH) = -60 µA, VCC = 5V ± 10%. VOH = 2.4 V
source current (IOH) = -25 µA VOH = 0.75 VCC
source current (IOH) = -10 µA VOH = 0.9 VCC

Port pin in this mode is used to switch 'ON' NPN tr.
Eg code: setB p1.x

Doubt:
This shows different o/p high voltage rating. i need to know what does this signify in connecting a Transistor(NPN) to it.
Can this negative current drive the NPN transistors with presence of external pullups.


2)b
VOH1 Output High Voltage (Port 0 in External Bus Mode) at different source current ratings:
Source current (IOH) = -800 µA, VCC = 5V ± 10% VOH = 2.4 V
Source current (IoH) = -300 µA VOH = 0.75 VCC
Source current (IOH) = -80 µA VOH = 0.9 VCC

same Doubt as in 2)a

3)
Logical 0 Input Current(IIL) (Ports 1,2,3) = -50 µA when VIN = 0.45V
I would like to know what the above statement describes, having described the source and sink currents in 1 & 2.

4)
Logical 1 to 0 Transition Current(ITL) (Ports 1,2,3) = -650 µA when VIN = 2V, VCC = 5V ± 10%
HOw this should be taken care of while connecting the driver circuit to the port.

Thanking you all,
-suresh.