Serial Port Commands Available - AKG CEQ1/1 Manual

9. Serial Port Commands Available

The CEQ1/1 uses a modification of the typical one-to-one connection between two RS-232 com­
patible devices. The CEQ1/1 has both an RS-232 transmitter and receiver section. The transmitter
section is "tri-stated", or placed in a high impedance mode, until the particular device is ad­
dressed. To facilitate the simple parallel connection of multiple devices on a single RS-232 port, an
addressing scheme is employed to route commands from the host to the proper device. When a
device receives its address from the host computer, it temporarily turns on its RS-232 transmitter
long enough to send whatever data is requested by the host. In this way, multiple devices may
drive a single transmit signal back to the host, because only the addressed CEQ1/1 will turn on its
transmitter.
Valid address values are 128-254 (80h-FEh). 255 (FFh) is an invalid address and must not be used.
Because the CEQ1/1 will interpret any single data byte whose value is greater than 127 as an
address, single byte data (as opposed to addresses) sent from the host must be in the range of 0­
127. If a data value needs to be output that exceeds 127, two bytes are output such that the first
byte is the lower 7 bits of the 8 bit value, and the second byte is 1 if the MSB of the data byte is 1, or
0 if the MSB of the data byte is 0.
Each CEQ1/1 command must be preceded by the address of the device to be controlled. If a
device with the requested address exists on the system, it will respond by sending a "0' back to the
host. The following code fragment, in BASIC, would be used to get an "Acknowledge" name string
back from an CEQ1/1:
OPEN "COM1:9600,N,8,1" FOR RANDOM AS #1 LEN = 256
...
...
...
PRINT #1, CHR$(131);
DataByte% = ASC(INPUT$(1, #1))
string
PRINT #1, CHR$(1);
mand.
DataByte% = ASC(INPUT$(1,#1))
Name$ = INPUT$(DataByte%,#1)
The first PRINT and INPUT$ sequence must precede every command sent, even if the command is
sent to the same CEQ1/1 as the previous command. The following is a listing of available com­
mands grouped based on the CEQ1/1 function to which the commands are related. The word
"Host" in the command descriptions means the IBM PC or compatible to which the CEQ1/1 is
connected.
There are several "status" flags that may be set by the host computer. Those flag commands that
store the new value in EEPROM will continue to have the new value even if the power to the
CEQ1/1 is turned off.
CEQ1/1 und CEQ1/1BB
'Open com port, 1 for 9600 baud, no
'parity, 8 data bits, 1 stop bit.
'Output the device address.
'Receive "0" byte. The ASC function
'is used to convert the received
'data to numeric data.
'Output the "Acknowledge" com­
'Receive the length of the
'acknowledge string
'(3 for the CEQ1/1).
'Receive the name string ("EQ1/
'EQ2")
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