Product Alert #6
STARLOG SOFTWARE PACKAGE - Modem 6300A - V1.8 & 2.10
DOS 6.0 & WINDOWS 3.1 - SmartDrive 4.1
17 June 1993
6.1 Communications Errors - using DOS 6.0 & Windows 3.1
Problem
SmartDrive 4.1, as installed by the default installation procedure of DOS 6.0 and/or Windows 3.1, uses write caching “Lazy Writes”. This causes communication errors when PDLIO is communicating with data loggers. PDLIO must have exclusive use of the CPU whilst communicating, otherwise UART overrun will occur. SmartDrive, with write caching enabled, “steals” the CPU from PDLIO when performing the deferred disk write, thereby destroying the continuity of PDLIO’s UART servicing.
Symptom
Error messages “*** Timeout on input ***” and “communication error” occur during unloading 8K or more of logged data. The error messages repeat about every 8K (whenever a write to the .DMP file occurs). The unload procedure retries and continues correctly. The unloaded data is correct.
Correction
In systems using SMARTDRV.EXE 4.1 (or later) turn write caching “Lazy Writes” OFF on the drive that holds the unload .DMP files before starting the PDL Software Package. The following command sequence may be used to perform this task:-
REM In this example C: is the drive used for unload .DMP files
REM Turn SmartDrive "Lazy Writes" OFF
SMARTDRV C
REM Begin PDL Software Package
CD\STARLOG
PDL
REM Turn SmartDrive "Lazy Writes" ON again
SMARTDRV C+
Notes
- After reading the warning notes in the DOS/WINDOWS installation files about resetting and turning of your computer if write caching is enabled, you may consider it prudent to change the default installation parameter for SmartDrive in your AUTOEXEC.BAT file to disable write caching on you hard disk drives altogether.
- Write caching is not the default installation setting for floppy disk drives.
- Network drives do not use SmartDrive.
6.2 Using the PDL Software Package from Windows 3.0 or 3.1
Problem
The PDLIO needs exclusive use of the CPU, therefore the .PIF file must be set to “EXECUTION = EXCLUSIVE” otherwise loading or unloading a data logger will fail.
Symptom
Error messages “*** Timeout on input ***” and “communication error” occur during loading or unloading a data logger in Windows.
Correction
The PDL Software Package runs under Windows 3.0 or 3.1 as a DOS task that has the “EXECUTION = EXCLUSIVE” parameter setting in the .PIF file. (Logger Loading & Unloading WILL FAIL if the .PIF file setting is “EXECUTION = BACKGROUND”.) Also ensure “Lazy Writes” are disabled as described above.
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