Systems Reference Library - All about the IBM 1130 Computing ...

LCCB Data Buffer Address WordThe data buffer address word is the fourth word inthe LCCB and is used to store the core storageaddress to or from which the next data character isto be transferred. When initializing the LCCB priorto activating the channel, the program places thestarting address of the data buffer associated withthe operation in the data buffer address word. Eachtime the byte count is increased to an even number,the data buffer address is increased by 1. Thisprocedure allows packing of two data bytes per corestorage word.LCCB Channel Sense WordThe channel sense word is the fifth word in the LCCBand is used by the adapter to store indicators thatdefine the cause of a channel interrupt to the program.Whenever a channel interrupt is generated, theadapter posts the interrupt condition(s) in the channelsense word and deactivates the channel. Whilethe channel is inactive, the contents of the LCCBare not modified by the adapter and are available forprogram interrogation.The individual indicators in the channel senseword are described next.SEQUENCE NORMAL END: This status indicator isturned on when a read or write sequence initiated bythe program reaches an ending point, and the AS ordevice status associated with the end indicates normalend status.SEQUENCE UNUSUAL END: This status indicator isturned on when a read or write sequence initiated bythe program is prematurely terminated as a resultof a request from the AS or device. The reason forthe termination is defined by the AS or device statusstored in the data/status/guidance field in word 2 ofthe LCCB. If the AS or device status indicatesdiagnostic mode, sequence unusual end is also turnedon.AS ADDRESS CHECK: This status indicator isturned on if an error is detected in a returning channelframe AS address byte. An AS address checkcauses the returning channel frame in which the erroris detected to be stored in the error framefields (LCCB words 6 and 7) for use in error recovery.DEVICE ADDRESS CHECK: This status indicator isturned on if an error is detected in a returning channelframe device address byte. A device addresscheck causes the returning channel frame in whichthe error is detected to be stored in the error framefields (LCCB word 6 and 7) for use in error recovery.FRAME CONTROL CHECK: This status indicator isturned on if an error is detected in a returning channelframe control byte. A frame control checkcauses the returning channel frame in which the erroris detected to be stored in the error frame fields(LCCB words 6 and 7) for use in error recovery.DATA CHECK: This status indicator is turned on ifan error is detected in a returning channel framedata byte. A data check causes the returning channelframe in which the error is detected to be stored inthe error frame fields (LCCB words 6 and 7) for usein error recovery. The AS response and channelcommand fields in the error frame are not validwhen a data check occurs; that is, they do not reflectthe contents of the returning channel framecontrol byte.BYTE COUNT EXCEEDED: This status indicator isturned on during a read operation if an attempt ismade to store an additional data byte after the bytecount has been decreased to 0. Byte count exceededindicates that the input data buffer assigned is toosmall for the incoming data.UNCONDITIONAL INTERRUPT: This status indicatoris turned on if the unconditional interrupt controlbit in word 2 of the LCCB is on when a returningchannel frame arrives for processing. Unconditionalinterrupt causes the returning channel frame to bestored in the error frame fields (LCCB words 6 and7).DATA STORAGE PROTECT: This status indicator isturned on if an attempt is made to store a data bytein a data buffer location that is storage protected.CHANNEL TIMED OUT: This status indicator isturned on if a channel timer count overflow conditionis indicated. The overflow condition is indicated bybit 0 of the LCCB channel timer count word being on.Channel timed out indicates that the channel has beenunsuccessfully attempting to complete a data transferoperation for a period of time longer than allotted bythe program.2790 Adapter 239