High-Performance SAB 80C517A/83C517A-5 8-Bit CMOS Single ...

SAB 80C517A/83C517A-5I/O PortsThe SAB 80C517A has seven 8-bit I/O ports and two input ports (8-bit and 4-bit wide).Port 0 is an open-drain bidirectional I/O port, while ports 1 to 6 are quasi-bidirectional I/O portswith internal pull-up resistors. That means, when configured as inputs, ports 1 to 6 will bepulled high and will source current when externally pulled low. Port 0 will float when configuredas input.Port 0 and port 2 can be used to expand the program and data memory externally. During anaccess to external memory, port 0 emits the low-order address byte and reads/writes the databyte, while port 2 emits the high-order address byte. In this function, port 0 is not an open-drainport, but uses a strong internal pull-up FET. Port 1, 3, 4, 5 and port 6 provide several alternatefunctions. Please see the "Pin Description" for details.Port pins show the information written to the port latches, when used as general purpose port.When an alternate function is used, the port pin is controlled by the respective peripheral unit.Therefore the port latch must contain a "one" for that function to operate. The same applieswhen the port pins are used as inputs. Ports 1, 3, 4 and 5 are bit- addressable.The SAB 80C517A has two dual-purpose input ports. The twelve port lines at port 7 and port8 can be used as analog inputs for the A/D converter. If input voltages at P7 and P8 meet thespecified digital input levels (V IL and V IH ) the port can also be used as digital input port.In Hardware Power Down Mode the port pins and several control lines enter a floating state.For more details see the section about Hardware Power Down Mode.Semiconductor Group 49