

The information contained herein, is solely for the use and 
benefit of EXABYTE customers.  It is not intended for 
distribution beyond the internal use of our customers.


SERVO CODE UPGRADE DESCRIPTIONS

Ver. 3.4  10/8/91B019 thru C033



Version	Date			

B019	9/14/89

Added delay to UNLOAD before generating COMMAND COMPLETE if door 
was open when UNLOAD is received.		

Timing to perform drum servo selftest is too close to the 
starting of the drum.  Some likelihood of receiving NO DRUM TACH 
or DRUM MOTION FAILURE.

	SOLUTION:	Increased delay from 4 to 6 seconds.

Added a status byte relating to REEL MOTION FAILURES.

	SOLUTION:	Data on process at time of failure includes: 
LOAD, UNLOAD, REWIND, CAPSTAN MOTION.

Tape may be damaged by drive trying to unload a tape when a reel 
motion failure is detected.

	SOLUTION:	Routines modified to prevent tape unload when 
error detected during load or unload.

Tape may be damaged by drive trying to respond to a reset after a 
REEL MOTION FAILURE.

SOLUTION:	Functions modified to go loaded state and 
then unload.  during transition to unloaded 
state the operation of the reel motor can be 
verified.		

Idler gear damage may occur if the reel motion changes direction 
at PBOT on the clear leader.

SOLUTION:	REWIND modified since the state of idler gear 
is not always known.

Cleaning cartridges may act as regular tape cartridges.

SOLUTION:	Routing modified.

Positioning errors may occur with 4$24 code.

SOLUTION:	Code modified to check for ATM's and if 
found, move forward to DTM track 3.

Modified PWM test by a factor of 5 to speed up testing of the 
servo card.




Cleaning tape may wind onto the supply reel if cleaning tape is 
too translucent. (Due to cleaning fluid).

SOLUTION:	Modified LOAD command.

Reduced tape tension transient when REWIND is initiated.

SOLUTION:	Modified voltage ramps.

Certain data pattern sequences resulted in false ATM detection 
which gave 09 and 89 errors.

SOLUTION:	Subroutine modified.

Manufacturing saw a high number of tracking retries during final 
test.

SOLUTION:	Modified capstan servo gain to improve 
performance during high friction periods.

Modified the offset command to determine the value of tracking 
position in order to optimize to offset tracking re-read 
sequence.

Enhanced the offset command to eliminate minor differences 
between drives and/or tapes.

Modified the tracking servo algorithm to better compensate for 
mechanical friction effects.

=================================================================
C020A	11/13/89

Generic Servo merged with another unique configuration code line.

Possibility exists to detect the same ATM twice.

SOLUTION:	Routine modified to clear ATM detect flag if 
detected.

Routine modified to add debug information to monitor dumps about 
drum tach, drum motion, and drum idle time.

=================================================================
C020B	11/21/89

New DRUM_TEST routine with re-try.

Internal development use only.

================================================================
C020C	2/13/90

Unique configuration containing End-of-Data feature.

A cleaning cartridge or a defective tape was not always ejected.


SOLUTION:	Code modified.

Algorithm to detect defective cartridges was modified.

If a cartridge cannot be wound forward from PBOT while loading it 
is defective.

SOLUTION:	Modified LOAD command to immediately unload 
and eject tape.

================================================================
C020D	3/5/90

Internal development use only.

Generic servo with fixes.  Bus reset while loading a new tape is 
now handled.  Handles loading a tape positioned near PBOT.  
Handles cleaning tapes and reel tach errors more reliably.

================================================================
C020E	3/20/90

Internal development use only.

Minor fixes in C020D.

===============================================================
C020F	4/10/90

Timing window error during bus reset.

SOLUTION:	Timing error fixed

===============================================================
C020G	4/4/90

Based on C020B.  Added autosizing feature.

==============================================================
C021	5/12/90

Based on C020F.

Reel tack failed under certain conditions.

SOLUTION:	Watchdog timings changed.

Problem unloading 112m tape PEOT.

=============================================================
C022	5/18/90

Based on C021.

Contains Alpha version of High Speed Search (HSS).
Added Read Position and Locate functions.

=============================================================
C023	5/24/90

Beta release of HSS.

Problem of HSS when LOCATEing near LBOT, especially in the 
reverse direction.

=============================================================
C024	6/8/90

Generic servo for HSS, Autosizing, and End of Data.

Diagnostic routines are removed from previous development code 
versions.

===============================================================
C025	7/2/90

Based on C024.

Problem with HSS at end of 112m tape.

SOLUTION:	HSS algorithm modified to ensure desired 
location near end of tape.

HSS commands are rejected if SERVO board is not an SX model.

================================================================
C026	8/8/90

Based on C025.

HSS LOCATE function is further refined to be faster and more 
reliable by revised algorithm based on lab data and using high 
speed capstan repositioning after spooling.

Low Servo amplitude now has comparison with ATM threshold.

=================================================================
C027	8/30/90

Internal development use only.

POSITION command now rejected if the drive is not an HSS model.

SOLUTION:	Previous implementation set bits but did not 
interrupt the controller correctly.

Some test commands added back into Generic for manufacturing 
testing.

=================================================================
=
C028	9/15/90	

Internal development use only.

=================================================================
==
C029	10/18/90

Generic Release EXB-8200.

=================================================================
==
C029z	

Unique Configuration

HSS routines now start the reel motor during LOCATE command 
regardless of tach count.

SOLUTION:	Prevents reel motion fault from occurring if 
desired location is very close to current 
location.

Some drives exhibited location overshoot during HSS due to loose 
tape pack at high speed.

SOLUTION:	Tach count search offset window was modified.

Some unnoticed reel motion failures occurred during a LOCATE.

SOLUTION:	Routines modified to be active in both REWIND 
and LOCATE instead of just REWIND.

In some cases the drive has an unknown null state.  This may 
cause the drive to search in the wrong direction initially.

SOLUTION:	Routine added always find a known mode state 
from a null state.

=================================================================
==
C02A	10/31/90

Minor change to tape tension during code enhanced file mark 
processing.

=================================================================
=
C02B	12/3/90

GENERIC RELEASE for 2600 level of EXB-8200 - BASELINE RELEASE

Modified the definition for foreign tape format.  Servo code can 
now identify a non 8200 tape and send a flag to the MX code.

SOLUTION:	Code enhanced.

Sometimes the reel motor stalled if a REWIND near PBOT of 112M 
tapes occurred.

SOLUTION:	Increased maximum reel motor voltage.

Sometimes the reel motor ran to slowly during REWIND.


SOLUTION:	Increased maximum reel motor voltage allowed 
during REWIND.

Sometime the REWIND motion does not start soon enough.

SOLUTION:	Adjusted timing parameter window.

Code enhanced to improve the tension transient response of the 
takeup reel after a reverse-to- forward transition.

Sometimes the drive did not detect a reel motion failure during 
REWIND or HIGHSPEED SEARCH.

SOLUTION:	Code corrected to always detect a reel motion 
failure.

Sometimes the drum does not start correctly.

SOLUTION:	Modified the restart timing window to allow 
capacitor discharges to occur before restart 
is activated.

=================================================================
=
C02C	12/11/90

An excessive tape loop can be formed when a reel motion failure 
occurs or a re-start is triggered during a HSS motion.

(This version of code not released to the field).

SOLUTION:	Modified the motion test routine to 
discriminate between 1x and HSS tape speeds 
when comparing elapsed distances.

=================================================================
==
C02D	12/17/90

Corrected small bug in C02C.

=================================================================
==
C02E	2/13/91

A glitch may cause the drum motor voltage to be the minimum value 
instead of the maximum value upon startup.

Error recovery proceedure added to correct the problem.  Drumtest 
routine modified.  Function is transparent to MX or Host.

=================================================================




C02F	2/13/91
Rev 2 of C02E.

Added a drum recovery flag to signal that the recovery proceedure 
described in C02E has been performed.  

Diagnostic/debug function added for monitor recognition.

================================================================
C030	3/1/91

Modified the GOTRACK command and other routines which reset the 
LSI watchdog timer during HEAD SYNC to prevent drum motion 
failures from hanging the synchronization loops which rely on 
HEAD SYNC.  If the drum is not spinning properly, a DRUM MOTION 
failure will be detected and reported to the MX up and a normal 
SERVO ERROR hardware failure should result.
=================================================================
C031	3/20/91

A broken or glitching BOT sensor can cause too much tape to spill 
into the drive before stopping.
Modified the REWIND command to properly handle this condition by 
limiting the amount of repositioning that can be performed before 
a BOT SENSOR failure error is generated.
=================================================================
C032	4/20/91

Modified the WATCHDOG subroutine to change the sequence of steps 
in re-starting the counter and clearing the T1 Overflow Interrupt 
Flag so that it is not possible to get and unwanted interrupt and 
cause a timing error in the software watchdog operations.
=================================================================
=
C033	4/24/91

Modified the routine RL_REWIND to discriminate between 15m, 54m, 
and 112m cartridge sizes when setting the reel motor control 
voltage.  This change allow more flexibility in optimizing 
performance/reliability for each cartridge type during high-speed 
reel-controlled motions.  The 15m reel voltage is reduced to 
1.96V




NOTES:

	1.	C024 and later is compatible with all MX code later than 
4$25.  For optimum performance, use MX with autosizing 
for these servo versions.
2.	C02A/B/D/E/F and C021 are compatible with all MX code 
later than 4$25 that DO NOT have Autosizing, End of Data 
(EOD), or High speed Search (HSS).
3.	CO20C is compatible with MX EOD 4$25 and later with DO 
NOT contain Autosizing or HSS.
4.	C020G is compatible with all MX 4$25 and later which DO 
NOT have EOS or HSS.
5.	C022 and C023 are compatible with MX HSS 4$25 which DO 
NOT have Autosizing or EOD.
6.	C027, C028, C029, C02A are not available for new build 
products.
7.	C02B is only compatible with 2600 or later MX code.
=================================================================
==
C034		6/26/91

1.	Added de-glitch code to the sensing of BOT and EOT in the 
REWIND and CHK_BOTEOT routines.  The code now performs two 
sensor reads separated by a 50 ęsec delay.  If the sensor 
readings are different, they are discarded.

2.	Modified the following SELFTEST routines to eliminate 
possible hang conditions or timing exposures which could 
result in false error detection:

Removed cartridge insertion timing sensitivity from:
SNSRTEST		(optical and mechanical sensor test)
CURRENT_TEST	(write, servo and erase current test)
RTACHTEST		(reel motor/reel hub tach test)

Removed potential hang conditions which could result from 
faulty hardware:
HSYNC_TEST		(servo LSI/ HEAD SYNC, QSYNC test)
ZONE_TEST		(servo LSI/ servo data zone timing 
test)
ADC_TEST		(ADC timing and analog data path 
voltage test)
CURRENT_TEST	(write, servo and erase current test)

3.	Added reel motor idler gear flip transition control to 
RTACHTEST when starting and reversing the direction of the 
reel motor to perform the test.  This prevents potential 
idler gear malfunction and conforms to motor timing used in 
all functional operations.  This change requires that the 
drum servo (HEAD SYNC) be functional during the test, 
therefore the sequence of test routines in SELFTEST was 
changed to accommodate this requirement.

4.	Restored the reel control voltage levels for rewind 
operations for all cartridge sizes to the REV C032 levels.  
This only affects the operation of 15m and 54m cartridges.

=================================================================
====
