Adcom manual A720B and A723, but see also the comments in Remote on

	CHAPTER 4
	Using terminal commands
APPLIES TO	A720B and A723, but see also the comments in “Remote” on
	page 49.
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 14.

47

Command Code

Port Number

Figure 14. Control Byte Layout

•The Port Number selects a the port that will be affected by the command. For the A720/A723, only 0000 and 0001 are accepted.

•The Command Code specifies the operation that will be applied to the selected port.

Table 5 shows the command codes definitions.

Table 5. Command Code Definitions

Code	Description	Parameters	Returns
0000	RDP – Read Data Port. This command reads the	None	A 16-bit integer and the
	whole 16-bit port and returns its value; the Port		result (OK or ERROR).
	Number has no significance for this command.
0001	RDDR – Read Data Direction Register. This com-	None	A 16-bit integer and the
	mand reads the whole 16-bit Data Direction		result (OK or ERROR).
	Register and returns its value; the Port Number
	has no significance for this command.
0010	CAI – Configure the port specified by Port Num-	The port number.	Result (OK or ERROR).
	ber as input (acts upon the Data Direction Regis-
	ter).
0011	CAO – Configure the port specified by Port	The port number.	Result (OK or ERROR).
	Number as output (acts upon the Data Direction
	Register).