Samsung manual Port Data Registers, S3F80JB I/O Port Data Register Format

I/O PORTS S3F80JB

PORT DATA REGISTERS

Table 9-4 gives you an overview of the register locations of all four S3F80JB I/O port data registers. Data registers for ports 0,1,2 and 4 have the general format shown in Figure 9-1.

NOTE

The data register for port 3, P3, contains 6-bits for P3.0–P3.5, and an additional status bit (P3.7) for carrier signal on/off.

Table 9-4. Port Data Register Summary

Register Name	Mnemonic	Decimal	Hex	Location	R/W
Port 0 data register	P0	224	E0H	Set 1, Bank 0	R/W
Port 1 data register	P1	225	E1H	Set 1, Bank 0	R/W
Port 2 data register	P2	226	E2H	Set 1, Bank 0	R/W
Port 3 data register	P3	227	E3H	Set 1, Bank 0	R/W
Port 4 data register	P4	228	E4H	Set 1, Bank 0	R/W

Because port 3 is a 6–bit I/O port, the port 3 data register only contains values for P3.0 – P3.5. The P3 register also contains a special carrier on/off bit (P3.7). See the port3 description for details. All other I/O ports are 8–bit.

MSB

.7

.6

.5

.4

.3

.2

.1

.0

LSB

Pn.7

Pn.6

Pn.5

Pn.4

Pn.3

Pn.2

Pn.1

Pn.0

NOTE: Because port 3 is a 6-bit I/O port, the port 3 data register only contains values for P3.0-P3.5.

The P3 register also contains a special carrier on/off bit (P3.7). See the port 3 description for details.

All other S3F80JB I/O ports are 8-bit.

Figure 9-1. S3F80JB I/O Port Data Register Format

9-4