BASIC COMMUNICATIONS PROTOCOL FOR HOST PROCESSOR AND UTS 30

3.5.1. Rules for Basic Communications Between Host Processor and UTS 30

The following rules define the basic communications procedures between the host processor and the UTS 30. These rules are based on the assumption that no peripherals are involved, only one station in the poll group is being used, and the program attention keys are not being used.

• UTS 30 rule 1:

The station responds only to error-free polls

• UTS 30 rule 2:

The station expects an acknowledgment to any message it sends in response to a poll except the no-traffic message.

• UTS 30 rule 3:

The station responds to a poll that includes an acknowledgment to a previous text message in one of two ways, depending on the message length:

1. When the total message length from the station exceeds 4096 bytes, a station will send consecutive text blocks until the transmission limit* of the screen is satisfied. Thus, the response to a poll with acknowledgment of the previous text block is to send a no-traffic message. (Except for the last text block in the sequence, the message format will include an ETB character indicating more data is to come.)

2. When the total message length from the station does not exceed 4096 bytes, a station will not send consecutive text blocks. Thus, the response to a poll with acknowledgment of the previous message is to send a no-traffic message.

• UTS 30 rule 4:

The station acknowledges in its next poll response any error-free host processor message containing an STX (text message), message-wait, or disconnection command.

• Host processor rule 1:

Upon sending a text message to a station, the host processor must poll to verify proper receipt of the text. This poll must occur before any other text is sent to that poll group.

If the UTS 30 does not respond with an acknowledgment verifying proper receipt of the text, the host processor must resend the message.

• Host processor rule 2:

The host processor must send a poll with acknowledgment to a station that has sent an acknowledgeable response before the host processor can send a text message to that station.

*Normally, a full-screen message will not exceed 4096 bytes; however, it is possible in UTS 30 operation, by use

UP-9799 Rev. 1

SPERRY UTS 30 SINGLE STATION System Reference

3.5.2. Examples of UTS 30 Text Message Sequences

Example Sequence 1:

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The following message sequence applies UTS 30 rules 1, 2, and 3 when the total message length is less than 4096 bytes.

In this sequence, it is assumed that the operator has pressed the transmit key on a station whose RID is "1" and SID is "a."

1. SQH 1 P p ETX BCC

2. SQH 1 a p STX data ETX BCC

3. SQH 1 P p OLE 1 ETX BCC

4. EQT EQT ETX BCC

Explanation:

1. The host processor sends a general traffic poll to a poll group whose RID is "1."

2. The poll response is UTS 30 text from the station whose RID is "1" and SID is "a." (See UTS 30 rule 1.)

3. The host processor sends a general traffic poll with acknowledgment (OLE 1 ), signifying to the station that the host processor correctly received its text message; that is, the UTS 30 text message did not contain any characters with incorrect parity and the BCC in the UTS 30 text message matched the BCC accumulated by the host processor. (See UTS 30 rule

2.)

4. The station does not send consecutive message sequences when the message block is less then 4096 bytes; therefore, the response from the station must be a no-traffic message.

(See UTS 30 rule 3.) Example Sequence 2:

The following message sequence applies UTS 30 rules 1, 2, and 3 when the total message length is more than 4096 bytes.

In this sequence, it is assumed that the operator has pressed the transmit key on a station whose RID is "1" and SID is "a."

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1. SOH 1 p p ETX sec

2.

3. SOH 1 p p OLE 1 ETX sec

4.

5. SOH 1 p p ETX sec

6.

7. SOH 1 p p OLE 1 ETX sec

8.

Explanation:

SPERRY UTS 30 SINGLE STATION System Reference

~

4 SQH 1 a p STX data ETS ETX SCC

•

•

EQT EOT ETX ETX

•

•

^{SQH 1 a p} STX data ETX SCC

~

....

EQT EOT ETX BCC

UP-9799 Rev. 1

1. The host processor sends a general traffic poll to a poll group whose RID is "1."

2. The poll response is UTS 30 text (4096 bytes) from the station whose RID is "1" and SID is "a." The response from the station includes an ETB indicating more data is to come. (See UTS 30 rule 3.)

3. The host processor sends a general traffic poll with acknowledgment (OLE 1 ), signifying to the station that the host processor correctly received its text message; that is, the UTS 30 text message did not contain any characters with incorrect parity and the BCC in the UTS 30 text message matched the BCC accumulated by the host processor. (See UTS 30 rules 2 and 3.)

4. No traffic.

5. General traffic poll.

6. The UTS 30 whose RID is "1" and SID is "a" responds to the general traffic poll with acknowledgment by sending the remaining text. in the message.

7. The host processor sends a general traffic poll with acknowledgment (OLE 1 ).

8. Since the message block is now complete, the response from the station must be a

no-UP-9799 Rev. 1

SPERRY UTS 30 SINGLE STATION System Reference

3.5.3. Example of Host Processor Text Message Sequence

The following message sequence applies UTS 30 rules 1, 2, and 4 and host processor rules and 2.

1. SOH a p STX data ETX BCC 2. SOH P p ETX BCC

3. SOH 1 a p D LE 1 ETX BCC

4. SOH 1 a p OLE 1 ETX BCC

5. EQT EOT ETX BCC

Explanation:

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1. The host processor sends a text message to a station whose RID is "1" and SID is "a."

This station must not be expecting an acknowledgment; that is, its previous poll response (assuming it is the only station being used in the poll group) would have been a no-traffic message.

2. The host processor sends a general traffic poll to verify that the station received the text message correctly. (See host processor rule 1.)

3. The acknowledgment (OLE 1) indicates that the station correctly received the text message from the host processor; that is, the text message contained no characters with incorrect parity and the BCC in the text message matched the BCC accumulated by the UTS 30. (See UTS 30 rule 4.)

4. The host processor must acknowledge any UTS 30 message other than a no-traffic message. (See host processor rule 2.)

5. The UTS 30 correctly received the poll-with-acknowledgment message from the host processor and responds with a no-traffic message.

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