2.2 The IBM 7171 ASCII Device Attachment Control Unit - Index of

BOC DC us OCBITSo2 3 4 5 6 7Bit Name Significance0 Command Reject (CR) Set if the IBM 7171 has received aninvalid command.1 Intervention Required Set if a command, other than Sense,(IR)was addressed to a device that is unavailableor is in the "not ready" condition.2 Bus Out Check (BOC) Set if the IBM 7171 has detected badparity on any command or data typereceived from the channel.4 Data Check (DC) Set if the CC board sends a commandto the CPU board, but the addresseddevice is no longer attached.5 Unit Specify (US) Set if the sense bits resulted frompolling the RS-232-C interface.7 Operation Check (OC) Set when the IBM 7171 has receiveda valid command or order that itcannot execute as follows:1. SBA, RA, or EUA order specifiesan invalid buffer address.2. Write data stream ends before allrequired bytes of SBA, RA, EUA,or SF order sequences arereceived.3. The IBM 7171 received acommand chained to Select RB,Select RBP, Select RMP or SelectWRT command other than wasexpected; or the byte count of aWrite command after RBP orRMP was not equal to 4.Figure 6-12. Sense Bit DescriptionSense ID Command: The Sense ID command requests data transfer to the host.Four bytes of data are sent as follows:I FF I 32 I 74 I 1 D IChapter 6. IBM 71711/0 Interface to the Host System 6-19