I/O Supervisor/
Access Method Start I/O
1 Start I/O
I
CCW
Write (CC) WritE! (CC)
I
Read
I
TCU Write Data
(From Channel Program)
TCU Read Data
(Generated by 3270 CU) (Leading Pad and SYN Chars*)~
EDT
(Trailing Pad and SYN Chars*) Hardware - _ - 3270 CU Address Generated
3270 CU Address Device Address Device Address ENQ
(Interrupt: CE + DE + UC) (TCU Sense Bit: Timeout)
(Interrupt: CE + DE)
I ~
I Resp~nse
I (
1 )-U
1 I
RVI WACK (2) (3)
....
1
----t---
Write - - - " ' - - - EOT(5)'-1
----t---I---(
Interrupt: CE + DE)---r---Start I/O I
.... - - -... - _ Write
--~...--
EOT(6).I---... ---...
--Interrupt:CE
+DE)--_---II
Start I/O - - . - W r i t e (CC)
+
Command Sequence (7)I :
Read
I
I
*Only the critical framing characters (sync pattern and pad) are shown. All other framing characters are also hardware-generated as required. See SL General Information - Binary Synchronous Communications, GA27-3004 for a complete description.
Figure 14. Selection Addressing, Sequence/Response Diagram (Sheet 1 of 2)
58 3270 Component Description
Notes:
1. The 3270 CU will fail to respond to the addressing or polling sequence, causing a TCU timeout, for any of the following reasons:
., The 3271 is "unavailable" (has power off, is "offline", or is not attached).
• The 3271 is "unavailable" (is not attached, has power down, or has the Security Lock in the "off" position).
• Any character in the polling sequence is invalid.
• The characters in the polling sequence are out of order.
• The polling sequence is incomplete (less than seven characters).
• The 3270 CU address is incorrect in the write data stream.
r"
3271: The addressed device has pending status (excluding Device Busy and Device End) or is unavailable, the device-to-3271 buffer transfer was unsuccessful, the 3271 detected an internal parity or cursor check, or the addressed printer became "not ready" (out of paper, unrecoverable "hang", power off, or cover open). The SIS information is stored in the 3271, and the internal 32711device polling is stopped.3275: The 3275 has pending status, excluding Device Busy and Device End.
3. The addressed 3271 device or the 3275, including the 3284-3 Printer, is busy. No SIS information is stored. An RVI response takes precedence over a WACK response. A Specific Poll should be issued when Busy is received. A General Poll ignores the condition and proceeds to poll the next device.
4. The address has been successfully received, no status is pending, and, in the case of the 3271, the device-to-3271 buffer transfer is successfully completed.
5. Termination of attempted addressing sequence:
3271: Availability of valid status and sense information cannot be ensured unless a Specific Poll is issued to the responding device as the next addressing sequence issued to this 3271. Successfu I completion of a Specific Poll addressed to the responding device, a device selection addressed to any other device on the same 3271, or a General Poll addressed to the same 3271, is required to start the internal 3271 device polling operation.
3275: A Specific Poll to the 3275 retrieves the status existing at the time the RVI response was made.
6. Termination of attempted addressing sequence.
7. Refer to Figure 15 or 16 for the desired command sequence.
LEGEND:
(CC)
=
Chain Command (CC) Flag in CCW is set to 1.(Interrupt) = TCU - Generated interrupt (CE = Channel End, DE = Device End, and UC = Unit Check) (1) = Number in parentheses refers to note.
Figure 14. Selection Addressing, Sequence/Response Diagram (Sheet 2 of 2)
Remote Operations 59
I/O Supervisor/
CCW TCU Write Data TCU Read Data
Access Method (From Channel Program) (Generated by 3270 CUI
(Selection or Poll Seq or Previous Command Op)
Start I/O - - - Write (CC) - - - STX
I
Read
ESC
Command Code Text (1)
ETX
(BCC) Hardware Generated
No Response
(2)
... 4---1--
(I nterrupt: CE + DE + UC) _ _ ... 1 NAK (TCU Sense Bit: Timeout) (4,5)... -~---+---ll__-
(Interrupt: CE + DE)---1 1
Start I/O
L . . . I
---ll---
Write - - - - + - - - - E O T (6)EDT (3)
- I - - - + - - - + - - - ( l n t e r r u p t : CE + DE + U E)---.;~----....
Start I/O
I
Write (CC)--I--f
Poll Sequence to ]I L
Receive SIS BytesRead
ACK 1 or 0 (9)
WACK (7)
-I ----_~---....f---(Interrupt: CE + D E ) - - I - - - -....
Start I/O
L - I _ _ _ _ _
~--
Write---1----
EDT (8)Start I/O
(Terminate)
",_-_IIiIIIII _ _ Write _ _ , , _ _ _ EOT (8)
(Continue)
. . - - - W r i t e (eC) Read
I
I (10)
[
Command sequence]
I
such as Write Command Code andI
next block of textFigure 15. Write-Type and Control-Type Commands, Sequence/Response Diagram (Sheet 1 of 2)
60 3270 Component Description
Notes:
1. No text is transmitted on an EAU command transmission.
2. Command transmission was not successfully received because of invalid framing (STX or ETX missing). Causes timeout at TCU.
3. 3271: The 3271 is unable to perform the operation indicated in the command transmission because of a busy/unavailable device or one of the following 3271..cJetected check conditions:
a. receipt of an illegal command/order sequence, b. failure to decode a valid command,
c. an I/O interface "overrun", d. a parity/cursor check, e. an illegal buffer address, or f. a locked buffer.
In the case of the Copy command: Copy feature is not installed, "from" device is busy or has locked buffer, or CCC is missing.
The EOT response to a command transmission indicates that status information is stored in the 3271 and that internal 3271/device polling is stopped. To ensure retrieval of valid status, the program must issue a Specific Poll (addressing the device that was selected when EOT was generated) as the next addressing sequence to this 3271. Successful completion of a Specific Poll addressed to the responding device, a device selection addressed to any other device on the same 3271, or a General Poll addressed to the same 3271, is required to restart the internal 3271/device polling operation.
3275: The 3275 is unable to perform the operation indicated in the command transmission because of (1) a BCC error, (2) a busy 3275 (including the attached 3284-3 Printer), or (3) a 3275-detected check condition (receipt of an illegal command/order sequence or failure to decode a valid command or an I/O interface "overrun" or a parity/cursor check). A Specific Poll to the 3275 retrieves the status existing at the time the EOT response was made.
4. 3271: If a transmission problem causes both a 3271..cJetected check condition and a BCC error, the BCC error takes precedence over all other check conditions, and a NAK is transmitted to the TCU.
5. 3271: BCC error has been detected. The NAK response requests the program to repeat its last transmission.
Note: The 3275 responds with EOT if it detects a BCC error.
6. Response issued by the program to terminate the operation if the 3271 is unsuccessful in receiving a valid BCC following "n" attempts by the program to transmit the message.
7. If the Start Printer bit is set in the WCC or CCC, a WACK response indicates that the text transmission was successfully received (and, if 3271, that the 3271-to..cJevice buffer transfer was successfully completed) but that the printer is now busy and an additional chained command cannot be accepted.
If any of the conditions cited in Note 3 prevail, the EOT response takes precedence over the WACK response.
8. Normal termination of the operation by the program.
9. Command execution has been successfully completed and, in the case of the 3271, the 3271-to..cJevice buffer transfer is successfully completed.
10. Repeat the operation shown in this figure or in Figure 16 for the next command sequence.
LEGEND:
(CC) = Chain Command (CC) Flag in CCW is set to 1.
(Interrupt) = TCU - generated interruption (CE = Channel End, DE = Device End, UE = Unit Exception, UC = Unit Check).
(1) = Number in parentheses refers to note.
Figure 15. Write-Type and Control-Type Commands, Sequence/Response Diagram (Sheet 2 of 2)
Remote Operations 61
I/O Supervisor/
Access Method CCW
(Selection Sequence or Previous Command Op)
~ Start I/O