Xerox 7250, Reference Manual

Page 1: ...Rank Xerox Cartridge Disk System Models 7250 7251 7252 Reference Manual 90 3024 A...

Page 2: ...CODES Function Write Read report any transmissi on error at count done Seek Sense Check write Read if an error is encountered terminate the data transfer and report any transmission error ot the end...

Page 3: ...Rank Xerox Xerox Cartridge Disk System Models 7250 7251 7252 Reference Manual FIRST EDITION 903024A June 1973 Price 1 50...

Page 4: ...ymbol LN OPS Reference Manual Xerox 32 bit Computers 90 17 90 Symbol LN oPS Reference Manual Xerox 16 bit Computers 90 1051 Extended Symbol tN OPS Reference Manual Xerox 16 bit Computers 90 1052 Meta...

Page 5: ...lags Xerox Sigma 5 6 7 8 Service Cycles 9 Computers 20 Order Out 9 Sequence of Activity 20 Data Out 9 Data In 9 Order In 9 Terminal Order 9 Disk Organization 9 Tracks 9 4 OPERATIONS 27 Sectors 11 Cyli...

Page 6: ...rogram Cartridge Disk System Actions 21 4 State Transitions 12 9 Write Order 22 5 Orders 14 10 Read Order 23 6 Test Mode Selection 15 11 Seek Sense Order 24 7 Overflow and Carry Indicators and Conditi...

Page 7: ...hich may be any desired combination of Model 7251 7252 Disk Drives employ the Model 7254 Disk Cartridge as a storage medium Each controller ac commodates a storage capadty of up to 18 4 mi IIion bytes...

Page 8: ...38 msec average I A write protect feature ensures total fi Ie protection The simplified system design makes I O programming less complex than that required for conventional disk systems SYSTEM COMPON...

Page 9: ...ini mum configuration 2 3 mi lIionl bytes i One 7250 controller One 7251 disk drive One 7254 di sk cartridge i The maximum configuration 18 4 mi Ilion bytes is One 7250 controller Four 7252 di sk driv...

Page 10: ...milarly after the execution of a device order the con troller reports the type of termination e g channel end unusual end transmission error 4 Functional Description CARTRIDGE INITIALlZATION New cartr...

Page 11: ...ans of standard electromagnetic recording techniques One head functions on each disk surface In Figure 2 the heads are located toward the back of the spindle bowl and they appear physically as shown i...

Page 12: ...ment power is off On the 7252 disk drive the fixed disk is fitted beneath the spindle bowl and is magnetically and physically similar to the cartridge disk I O OPERATIONAL FlOW Figure 5 which illustra...

Page 13: ...e X 12 Read X 13 Test I O Control Doubleword Word address E DC I Byte count Pointer to the first word of the VO tabl Error flag Data chaining flag Interrupt flag Number of bytes to be tran lftitted In...

Page 14: ...execute orders X Ol Write X 02 Read X 03 Seek X 04 Sense X 05 Check write X I2 Read X 13 Test I O Command Doubleword Memory byte address Pointer to the first byte DC Data chaining flag IZE Interrupt a...

Page 15: ...nd stores the data beginning at the memory location pointed to by the address field of the lOCO The lOP terminates this cycle with or without a Terminal Order based on the channel condition ORDER IN T...

Page 16: ...p even numbered tracks 0 2 406 Bottom odd numbered tracks 1 3 407 Track 406 Track 404 2 o Typical track 1 A B 1 56cmsec D E F G H I 1 30 116 I fJSec fJSec t 1 byte tt 5 bytes 10 Disk Organization 1 15...

Page 17: ...n the next sector However if they do nor match the controller compares the converted track address with the cylinder address of the next sector Should the comparison fail a second time the contr ller...

Page 18: ...an address 408 An error condition also occurs if the disk I O program issues a Seek order to load the address register with the address of a nonexistent sector SYSTEM STATES Three possible conditions...

Page 19: ...lowing an HIO instruction an I O Reset or an lOP halt the controller is in the ready conclition RECOMMENDATIONS The following recommendations and suggested usage apply to the Cartridge Disk System 1 T...

Page 20: ...s been transmitted When a record requires more than one sector the controller automatically increments the track and sector addresses and continues writing in the next sector see Data Access in 14 Pro...

Page 21: ...ead order reads from the disk the number of data bytes specified by the byte count field in the lOCO The data will be stored in the I o Table in memory starting at the address indicated in the lOCO Th...

Page 22: ...frack address greater than 407 8 The device cou Id not complete the previous Seek order 9 The INITIALIZE switch in the multiple drive selection unit is incorrectly set CHANNEL END CONDITIONS I After r...

Page 23: ...sponse tr the execu tion of each I O instruction Tables 8 9 aile iO list the possible settings of the Device Status Byte for eac Vo in struction and the significance of each setting OPERATIONAL STATUS...

Page 24: ...ma 3 computers Table 8 Device Status Byte for SIO TIO and HIO Instructions Bit Position Function Value Significance 0 Interrupt pending 1 Set if an interrupt is pending issued but not yet acknowledged...

Page 25: ...revious Write order attempted to write on a disk that is write protected violation a track address greater than 407 was specified or the INITIALIZE switch on the multiple drive selection unit is on 4...

Page 26: ...d for either task This can reduce the transfer rate as much as 50 percent and can cause data overruns A hen immediate mode transfer techniques are used data transmission at the next available sector t...

Page 27: ...ngth indicator I I 1 r I I I I SetChonnel End 1 r lndic ator I I I I I I I I Advance to busy condition U E Signal unusvol end to disk VO program Signol data transmi ion error to disk VO program Signal...

Page 28: ...cotor Set dota overrun indicator Sum byte with parity check byte Nonoperationol is reset to operational at neft 5ector T E i U E Figure 9 Write Order Writ protect is reset when n_ oddre 4A 7 Inc emer...

Page 29: ...t ned sector Write protect i reset when new oddre 407 Increment oddr reght r 1 by one etor Set dora o errun I E t T E r u i nd i co t or _____I S t parity Of indicator Figure 10 Read Order no no y T E...

Page 30: ...Figure 11 Seek Sense Order 24 Additional Programming Considerations...

Page 31: ...un indicator Nono rotional is r_t to o rational at eXt sector _ t T E IIol U E I _ Figure 12 Check write Order Write protect is relMOt when new oddre 4CJ7 yes Read parity check byte T E i u E I Additi...

Page 32: ...d FAM Fast A c_ M t 8 Not After completing the test loop and setting test mode indicaton rfwr test mode i5 nr 26 Additional Programming Considerations Sense order Seek order Read order yes Figure 13 T...

Page 33: ...ed bock to LOAD the disk decelerates to a stop in about 15 seconds and the LOAD indicator will light I 1 _ After the operator moves the switch to LOAD the unload sequence is inhibited until the system...

Page 34: ...the disk is rotating lighted when the disk is rotating at 2400 rpm the read write heads are loaded and no condition prevents normal disk operations Not lighted when the LOAD RUN switch is set to LOAD...

Page 35: ...it need not be turned on and off under normal operating conditions If required in some installations the customer service engineer will turn on the power in others the operator may be required to turn...

Page 36: ...Figure 16 Power Distribution Fone Switch normal positio up I tm i f r i e 0 0 0 CD v II Ii Fig re 17 PT20C Prj ver Supply...

Page 37: ...re 21 11 Close the two cartridge holding clamps 12 Close the equipment drawer by sliding the drive into the cabinet 13 Set the LOAD RUN switch to RUN 14 Observe the light on the LOAD indicator go out...

Page 38: ...Figure 18 Opening Cartridge Holding Clamps Fig re 19 t moving Bottom Cover from Disk Figure 20 Looding and Unloading a Cartridge Figure 21 Placing Bottom Cover over Cartridge 32 Operati ng Procedures...

Page 39: ...y Clark Corporation LABELING CARTRIDGES Cartridges may be labeled for identification It is recom mended that the top surface of the cartridge be used for labeling although the outside of the bottom co...

Page 40: ...surfaces need be cleaned only when the disk is 34 Cartridge Procedures suspected of being the source of errors The procedure for cleaning disk surfaces is contained in the maintenance manual for the...