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14 Parallel input/output

The ST20-GP1 device has 6 bits of Parallel Input/Output (PIO), each bit is programmable as an

input or an output.

The input bits can be compared against a register and an interrupt generated when the value is not

equal.

14.1 PIO Port

Each of the bits of the PIO port has a corresponding bit in the PIO registers associated with the

port. These registers hold: output data for the port (POut); the input data read from the pin (PIn);

PIO bit conﬁguration register (PC1); and the two input compare function registers (PComp and

PMask).

All of the registers, except the PIn register, are each mapped onto three separate addresses so

that bits can be set or cleared individually.

The Set_ register allows bits to be set individually. Writing a ‘1’ in this register sets the

corresponding bit in the associated register, a ‘0’ leaves the bit unchanged.

The Clear_ register allows bits to be cleared individually. Writing a ‘1’ in this register resets the

corresponding bit in the associated register, a ‘0’ leaves the bit unchanged.

14.1.1 PIO Data registers

The base addresses for the PIO registers are given in the Memory Map chapter.

POut register

This register holds output data for the port.

POut

PIO port base address + #00

Read/Write

Bit

Bit ﬁeld

Function

POut0

Output data bit 0

POut1

Output data bit 1

POut2

Output data bit 2

POut3

Output data bit 3

POut4

Output data bit 4

POut5

Output data bit 5

Table 14.1 POut register format

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