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

Form GA26-5918-8Page Revised 10/1/70By TNL GN26-0263CE DIAGNOSTIC: These four indicators are used bycustomer engineers (CE's) for diagnostic purposes.The indicators are active only when wired by a CEand do not represent interrupt conditions nor causeinterrupts to the program. Therefore, one of theother ten interrupting conditions must occur tocause an update of the channel sense word, and thusstoring of the CE diagnostic indicators. The CEdiagnostic indicators are always off unless wired foruse by a CE.LCCB Address Word (Error Frame)The address word (error frame) is the sixth word inthe LCCB. This word is used by the adapter to storethe AS address byte and device address byte of areturning channel frame if an error is detected inany portion of the channel frame, or if unconditionalinterrupt is on in the channel control field (LCCBword 2). The address word (error frame) containsthe following fields:AS ADDRESS: This field is used to store the returningchannel frame AS address byte.DEVICE ADDRESS: This field is used to store thereturning channel frame device address byte.LCCB Control Word (Error Frame)The control word (error frame) is the seventh wordin the LCCB. This word is used by the adapter tostore the control byte and data byte of a returningchannel frame if an error is detected in any portionof the channel frame, or if unconditional interrupt ison in the channel control field (LCCB word 2). Thecontrol word (error frame) contains three fields,described next.AS RESPONSE: This field is used to store the ASresponse digit (bit positions 0 through 3) from thereturning channel frame control byte. If a datacheck causes the returning channel frame to bestored in the error frame field, the AS responsefield is not valid; that is, it does not contain the ASresponse digit from the returning channel frame.CHANNEL COMMAND: This field is used to storethe channel command digit (bit positions 4 through 7)from the returning channel frame control byte.Unless a transmission error occurs, this field shouldbe identical to the transmitted channel commandlocated in word 2 of the LCCB. If a data checkcauses the returning channel frame to be stored inthe error frame field, the channel command field isnot valid; that is, it does not contain the channelcommand digit from the returning channel frame.DATA/STATUS/GUIDANCE: This field is used tostore the contents of the returning channel framedata byte. The returning channel frame data bytemay contain data, status, or guidance, depending onthe channel command transmitted and the AS responseto the command.LCCB Channel Timer Count WordThe channel timer count word is the eighth word inthe LCCB. This word is used to specify the numberof times the channel can attempt data transfer to corncompletean operation before a channel interrupt tothe program is generated. The channel timer countis initially set by the program while initializing theLCCB and is then increased by 1 for each unsuccessfuldata transfer attempt after the channel is activated.An unsuccessful data transfer attempt is recognizedwhen a read command acknowledge with busy status,read null acknowledge, a write command acknowledgewith busy status, or a write null acknowledge is receivedin the returning channel frame.Bit position 0 of the channel timer count word isused to determine when a channel interrupt to theprogram is to be generated. This bit position is interrogatedeach time the channel timer count is increased.If bit position 0 is on, a channel timercount overflow is indicated which causes the adapterto generate a channel interrupt to the program, postthe condition in the channel sense word, and deactivatethe channel. Thus, the maximum count thetimer may reach before an interrupt is generated is32, 767.DATA ENTRY FORMATSThe format of data entry, as it appears in theassigned input data buffer, depends on which deviceenters the data. Figure 125 shows the data formatthat appears in the data buffer for each type of device.Three special characters -- transaction code,guidance, and status -- may be used during a dataentry. They are described in the following paragraphs.240