Black Box A/S-4 Manual De Usuario

To send data to the SNA computer, the data from the VDU should look like this:

Device

Selection

Start

or

End

of

Special

of

File

Control

File

1 STX

2

3 Data

4 ETX

1.  Start of File (SOF) character is selected by H Application Options menu.  This single

character command can be disabled (turned off) so that no SOF character needs to be
received before handling the incoming data from the VDU.

2. a  Device selection character indicates which device (card, disk, printer or console) the data

is from, if the data is in transparent form and which  Logical Unit (LU) should transmit
the data to the SNA host.  This character is not sent to the SNA host.  The following is
the Device Selection character with its assigned bits:

Bit

7

6

5

4

3

2

1

0

1

1

Y

X

X

1 = Outbound LU data
0 = Inbound LU data

1 = Transparent data

XX = 00 - Console Data

0 = Normal data

01 - Disk Data
10 - Card Data

Parity bit can be 0 or 1

11 - Printer Data

Y =  Do Not Care

Example:  Device selection character of “2”(X`32’) would cause the data to transmit to the SNA host as
normal card data by the inbound (VDU) LU.

2.b  Special Control (SC) character precedes some types of data mentioned below:

1)  SO(X`0E’) character readies the A/S-4 to receive new options following the SO 

character.  For this to work, the A/S-4 and the VDU must be set for a character length
of 8-data bits with no parity.  The contents of this string of options is described later.
The SO (X`0E’) character does not need to be preceded by the Start of File character
or followed by an End of File character.