User guide

CHAPTER 3

Performing Advanced Functions

DPE

38193 DPE 3 60 0

COMMAND PORT

APPLIES TO A720B, but see comments in “Remote” on page 36.

DESCRIPTION A complex command acting upon the I/O ports of a device.

PARAMETERS A control byte specifying the command, the bit of the port the

command is acting on, and two 16-bit parameters, depending on

the control byte; for some commands, one or both of them may be

missing. However, if they are needed for a certain command but

not given, null values are implied.

The control byte’s significance is shown in Figure 7.

Figure 7. Control Byte Layout

• The Port Number selects a the port that will be affected by

the command. For the A723S4, only 0000 and 0001 are

accepted.

• The Command Code specifies the operation that will be

applied to the selected port.

Table 4 shows the command codes definitions.

Command Code

Port Number

Table 4. Command Code Definitions

Code Description Parameters Returns

0000 RDP – Read Data Port. This command reads the

whole 16-bit port and returns its value; the Port

Number has no significance for this command.

None A 16-bit integer and the

result (OK or ERROR).

0001 RDDR – Read Data Direction Register. This com-

mand reads the whole 16-bit Data Direction

has no significance for this command.

None A 16-bit integer and the

result (OK or ERROR).