Intermec CV30 Intermec Terminal Emulator (ITE) Programmer's Reference Manual - Page 20

Erase Unprotected to Address (EUA), Insert Cursor (IC), About 3270 and 5250 Programming

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Chapter 1 - About 3270 and 5250 Programming Erase Unprotected to Address (EUA) The Erase Unprotected to Address (EUA) order inserts nulls in all unprotected buffer locations, starting at the current buffer address and ending at (but not including) the specified stop address. For the asynchronous data stream, the stop address is specified by address bytes "xxxx" which immediately follow the EUA order in the write data stream. For SNA/SDLC (non-Telnet), the stop address is specified by the two address bytes which immediately follow the EUA in the write data stream. If an invalid stop address is specified (that is, an address outside the range of the computer's display buffer) the following occur in random order: • The write operation is terminated at this point. • The character is not stored. • The computer recognizes this as an error condition and performs a clear memory operation. • The display buffer is set to nulls. • A clear AID character is transmitted to the computer control unit for forwarding to the host computer. When the stop address is lower than the current buffer address, the EUA order wraps from the end of the buffer to the beginning of the buffer and continues. When the stop address equals the current buffer address, all unprotected character locations in the buffer are erased (set to nulls). Insert Cursor (IC) The IC order changes the stored cursor address to the location specified by the current buffer address. The current buffer address does not change. For example, if the IC order is issued when the current buffer address is 320 and the present stored cursor address is 0 (zero), the cursor address changes from 0 to 320. The current buffer address at the end of this operation remains at address 320. If multiple IC orders appear in the write data stream, the last one encountered is used in subsequent operations. If the IC order is placed at a location past the end of display on the computer, the current buffer address will be updated so that the cursor address will be located on the display. At the end of write data stream, after all orders have been executed by the computer and all required data has been entered into the buffer, the stored cursor address determines which unprotected field should be displayed to the user first. The following algorithm is used: 1 The computer searches the buffer backward to find the first protected field attribute before the stored cursor address. Unprotected attributes are not considered. 2 The computer does a forward tab (or equivalent) to an unprotected field. 3 If a protected field attribute is not found before the first location of the display buffer is found (location 0), then an unconditional forward tab equivalent is executed to display the first unprotected field in the buffer. 8 Intermec Terminal Emulator (ITE) Programmer's Reference Manual

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Chapter 1 — About 3270 and 5250 Programming
8
Intermec Terminal Emulator (ITE) Programmer’s Reference Manual
Erase Unprotected to Address (EUA)
The Erase Unprotected to Address (EUA) order inserts nulls in all unprotected
buffer locations, starting at the current buffer address and ending at (but not
including) the specified stop address. For the asynchronous data stream, the stop
address is specified by address bytes “xxxx” which immediately follow the EUA order
in the write data stream. For SNA/SDLC (non-Telnet), the stop address is specified
by the two address bytes which immediately follow the EUA in the write data stream.
If an invalid stop address is specified (that is, an address outside the range of the
computer’s display buffer) the following occur in random order:
•
The write operation is terminated at this point.
•
The character is not stored.
•
The computer recognizes this as an error condition and performs a clear
memory operation.
•
The display buffer is set to nulls.
•
A clear AID character is transmitted to the computer control unit for forwarding
to the host computer.
When the stop address is lower than the current buffer address, the EUA order wraps
from the end of the buffer to the beginning of the buffer and continues. When the
stop address equals the current buffer address, all unprotected character locations
in the buffer are erased (set to nulls).
Insert Cursor (IC)
The IC order changes the stored cursor address to the location specified by the
current buffer address. The current buffer address does not change.
For example, if the
IC order is issued when the current buffer address is 320 and the
present stored cursor address is 0 (zero), the cursor address changes from 0 to 320.
The current buffer address at the end of this operation remains at address 320. If
multiple IC orders appear in the write data stream, the last one encountered is used
in subsequent operations.
If the IC order is placed at a location past the end of display on the computer, the
current buffer address will be updated so that the cursor address will be located on
the display.
At the end of write data stream, after all orders have been executed by the computer
and all required data has been entered into the buffer, the stored cursor address
determines which unprotected field should be displayed to the user first.
The following algorithm is used:
1
The computer searches the buffer backward to find the first protected field
attribute before the stored cursor address. Unprotected attributes are not
considered.
2
The computer does a forward tab (or equivalent) to an unprotected field.
3
If a protected field attribute is not found before the first location of the display
buffer is found (location 0), then an unconditional forward tab equivalent is
executed to display the first unprotected field in the buffer.