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I/O PORTS S3F80JB
9-4
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.
Pn.4
Pn.3
.7 .6 .5 .4 .3 .2 .1 .0MSB LSB
Pn.1
Pn.2
Pn.5
Pn.6
Pn.7
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