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Samsung S3F80JB User Manual

Page 242

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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

.0

MSB

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