UNISCOPE MODE (FXXXX-XX)READV-RRRR-RR
3. Communications Protocol
3.4. MESSAGE FORMATS
SPERRY UTS 30 SINGLE STATION
System Reference 3-7
Except for the no-traffic poll response, all text and nontext messages, from the host or the UTS 30, begin with the start-of-header (SOH) character. The SOH marks the beginning of the address sequence.
On synchronous communications lines, the SOH character must be preceded by a minimum of four SYN characters. The SYN function is described in detail in Appendix A. SYN characters will not appear in the message examples in this section; their presence, if necessary, is understood.
All messages end with the end-of-text character (ETX) and then the block check character (BCC).
The BCC character is described in 3.3.
3.4.1. Host Processor Poll Messages to the UTS 30
The host processor can send the following types of polls to the UTS 30:
• Status pol I
• Traffic pol I
• Selection poll
• Retransmission request The format of a poll message is:
SOH RID SID DID control characters ETX BCC NOTE:
The DLE control character changes the meaning of the control character immediately following it. DLE is therefore used to increase the number of available control characters; e.g., DLE ENO and DLE EOT.
3.4.1.1. Status Poll (ENQ or OLE 1 ENQ)
A status poll solicits any nontext message the station has to send. ENQ is used to solicit status from a station without acknowledging a previous message. OLE 1 ENO acknowledges a previous message and solicits status from the station. (DLE 1 ENO can also be sent in reverse order: ENO DLE 1.)
3.4.1.2. Traffic Poll (OLE 1)
A traffic poll solicits any message the station has to send, including text messages. The traffic poll can be specific or general. A specific traffic poll requests traffic from a particular station;
a general traffic poll requests traffic from a poll group.
DLE 1 in the message indicates that the host is acknowledging a previous UTS 30 message. If there is no need for the host to acknowledge a response, no control characters are necessary.
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3.4.1.3. Selection Poll
SPERRY UTS 30 SINGLE STATION
System Reference UP-9799 Rev. 1
The selection poll has a specific RID, a specific SID, and a specific DID. Its primary purpose is to select a peripheral and obtain peripheral status. Peripheral selection is discussed in 3.8.3.
A selection poll that needs an acknowledgment will contain DLE 1; otherwise, a selection poll will not contain a control character.
3.4.1.4. Retransmission Request (OLE NAK)
The retransmission request has a specific RID, a specific SID, and a general DID. The retransmission request causes the UTS 30 to resend its last response and thus plays an important role in recovery from line errors. Line error recovery is discussed in 3.7.
The retransmission request from the host to the UTS 30 will contain the DLE NAK control character.
3.4.2. Host Processor Text Messages to the UTS 30
The host processor sends four kinds of messages to the UTS 30:• Data messages
• Message waiting
• Disconnection
• Dump sequences
3.4.2.1. Data Messages (STX ---- ETX)
All text messages containing data are bracketed between the start-of-text (STX) and end-of-text characters. This is called the "message envelope." The content of data messages is the subject of Section 4.
The data message must be preceded by the addressing (routing) information discussed in 3.2.
The format is:
SOH RID SID DID STX data ETX BCC
3.4.2.2. Message Waiting (BEL)
The BEL code turns on the MESSAGE WAITING message and the alarm of the UTS 30 identified by the RID and SID in the message.
UP-9799 Rev. 1
SPERRY UTS 30 SINGLE STATION System Reference
3.4.2.3. Disconnection Message (OLE EQT)
SOH RID SID DID OLE EQT STX ETX BCC3-9
Note that DLE used with EQT indicates line disconnection. The disconnection command is discussed in detail in 3.10.
3.4.2.4. Dump Sequences to Interrupt UTS 30 Activity
If the UTS 30 is in a pending transmit condition, the host can force the UTS 30 to accept an incoming host message by clearing the pending transmit condition and overwriting the data to be transmitted. Any host message containing STX will perform a dump transmit.
Similarly, the host can force the UTS 30 in a print condition to accept host text by clearing the print condition and overwriting the data to be printed. The dump print sequence is:
SOH RID SID DID NUL . (40 ms) . NUL STX
The specific DID in the dump print sequence must be either a "terminate" DID (ASCII q, hexadecimal 71) or a "deselect" DID (ASCII r, hexadecimal 72).
3.4.3. UTS 30 Messages to the Host Processor
All UTS 30 messages are sent in response to a poll and are categorized as follows:
• Reply request
• No traffic
• Acknowledgment
• Traffic (data)
The general format of the UTS 30-to-host message is:
SOH RID SID DID control characters STX ETX BCC
Note the difference in the use of the address. The host uses the address to correctly route its message to the UTS 30; the UTS 30 includes its address in a message to the host to identify the source of the message. Reply requests, no-traffic messages, and acknowledgments do not need an STX; only data messages need STX.
3.4.3.1. Reply Request (OLE ENQ)
The reply request is discussed in 3.7. Its format is:
SOH RID SID DID OLE ENQ ETX BCC
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3.4.3.2. No Traffic (EOT)
SPERRY UTS 30 SINGLE STATION
System Reference UP-9799 Rev. 1
If the UTS 30 has no other appropriate response to send, it will send a no-traffic response. (This is the only UTS 30 response that does not require an acknowledgment from the host processor.) The format is:
EOT EOT ETX BCC
In this case, the redundant form, EQT EQT, is used to increase reliability.
3.4.3.3. Acknowledgment (DLE 1 or DLE
?)UNISCQPE mode protocol uses the OLE 1 code for acknowledgment. Note that it does not use the ASCII code ACK.
An acknowledgment from the UTS 30 will occur in one of two formats.
1. Text was received without error:
SOH RID SID DID DLE 1 ETX BCC
2. Text was received without error, but the requested peripheral device was busy:
SOH RID SID DID DLE 1 ETX BCC
3.4.3.4. Traffic
The UTS 30 can respond to either general or specific polls with traffic. The traffic response may or may not carry a OLE 1 (acknowledge) or OLE? (busy) with it. The traffic response can be any one, but only one, of the following conditions:
• Text message (data) from a station screen when a transmit condition exists.
• Program attention key codes when one of the UTS 30 program attention keys has been pressed.
• Status of the station or of a peripheral sent as the result of a selection attempt.
• Disconnection message from a UTS 30 screen.
3.4.3.4.1. Text as Traffic
Text as traffic will be sent in one of two forms:
1. The standard UNISCQPE mode format that indicates acknowledgment (optional), start of text, text, and end of text. This format is used for all text messages less than 4096 bytes long.
UP-9799 Rev. 1
SPERRY UTS 30 SINGLE STATION
System Reference 3-11
2. A unique UTS 30 format that indicates acknowledgment (optional), start of text, text, and end-text-block (ET8) - more text is to come - before ETX. This format is used for consecutive text blocks where the message is longer than 4096 bytes. See 3.5.1 for more information concerning consecutive text sequences.
SOH RID SID DID (OLE 1 or OLE ?) STX data ETB ETX BCC
3.4.3.4.2. Program Attention Key Codes as Traffic
Program attention key codes are single ASCII characters. See Tables 8-10 and 8-11 for the ASCII codes and their hexadecimal equivalents. These messages are transmitted to the host when the operator presses the MSG WAIT key or one of the program attention keys. The format is:
SOH RID SID DID (OLE 1 or DL 1) key code ETX BCC
3.4.3.4.3. Status as Traffic
The status response is a pair of ASCII characters, the first character of which is always OLE. See Table 3-1 for the ASCII codes and their hexadecimal equivalents. Status responses are discussed in 3.8. The message format is:
SOH RID SID DID (OLE 1 or OLE 1) status ETX BCC Table 3-1. Status Codes
Status ASCII Characters Hexadecimal Code
Peripheral status 1 (ready) OLE> 10 3E
Peripheral status 2 (not ready) OLE< 10 3C
Peripheral status 3 (error) OLE: 10 3A
Peripheral status 4 (no response) OLE= 10 30
Message queued OLE 4 10 34
Peripheral selection delayed OLE 5 10 35
POC test completed OLE 6 10 36
THRU (station through with OLE I 10 38
peripheral interface)
Text-available response to OLE 0 10 30
status poll
3.4.3.4.4. Disconnection Message as Traffic
The disconnection message is discussed in 3.10. The format is:
SOH RID SID DID OLE EOT ETX BCC
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SPERRY UTS 30 SINGLE STATION
System Reference U P-9799 Rev. 1