
                        Release Notes for
   DS21x4 PCI Ethernet / Fast Ethernet Adapter SCO Unix LLI driver

                     SUL310T - Release 03.10
                          14-Jan-1995


Copying the distribution files
------------------------------

Version 03.10 of the SCO Unix LLI driver for the DS21x4 PCI Ethernet
adapter is now available.

The distribution files are:

   SUL310TD.Z (15493)     - the compressed image of the distribution diskette
   TSUL_INS.TXT           - Installation Guide for the DS21x4 LLI driver
   TSUL_REL.TXT           - release notes for this release (this file)

   1.  Copy the file SUL310TD.Z to SUL310T.dd.Z on a SCO Unix machine.
       The number in parentheses near the file's name (above) is the checksum
       for the file. To verify, use:
          sum -r SUL310T.dd.Z
       and compare the results.                                   
   3.  Uncompress SUL310T.dd.Z to SUL310T.dd, using:
          uncompress SUL310T.dd
   4.  Copy the file to a diskette. To create a 3.5" floppy in drive 0, use:
          dd if=SUL310T.dd of=/dev/rfd0135ds18
       Mark the diskette: 
         DS21x4 PCI Ethernet Adapter LLI driver
         Rel.03.10








Version 03.10
-------------

New features and modifications:

1. Fix bug in updating CSR6 register during DS21140 autosense algorithm.
2. Update all driver's prefix from "DCE" to "dce"
3. Fix bug in updating the autosense information that was read from the SROM.
4. Add support to SROM version 3.0
5. Update driver to stop TX or/and RX machines while updating CSR6.
6. Update port selesct bit in CSR6 before SW.
7. Changes in space.c :
   
   In XXX_DC21140_SERIAL_MODE :
   XXX_SYM_SCR was changed to XXX_100TX
   XXX_SYM_SCR_FULL_DUPLEX was changed to XXX_100TX_FULL_DUPLEX
   add the options :
      XXX_100T4,
      XXX_100FX,
      XXX_100FX_FULL_DUPLEX,

8. Add support to MII PHY chips.
9. Add support to DS21140A

Limitations:

Following are the known limitations of version 03.10:

1. The driver supports up to 4 ports.
   Due to PCI BIOS limitations, the user must be very careful when 
   configuring multiple PCI boards. The chains are bound in the order 
   the BIOS finds the adapters on the PCI bus, therefore must make sure 
   that the chains are set correctly. This is particularly true for boards
   with PCI-PCI bridges, where the adapters are on a PCI bus with a bus
   number higher than zero and therefore are found by the PCI BIOS after
   all the devices on buses with lower numbers. 

   For example:

   In a system with two DS21x40-based PCI boards installed (A and B)
   two chains are created:

      sco_tcp->dce0
      sco_tcp->dce1

   Assuming the PCI BIOS finds board A before board B, dce0 will be bound to
   board A and dce1 to board B.

   Removing board A, or adding another board C (that will be found by the BIOS
   before A or B) will cause a shift in the bindings.

2. The driver support only boards that their SROM was programmed in the
   format of version 1.0, 3.0 and the boards that their SROM was programmed in 
   the classic version (32 bytes of Ethernet address and checksum).

3. The driver was tested with boards that have National PHY and boards that
   have Broadcom PHY.
   When setting the connection in boards with Broadcom PHY to 100T4 connection,
   the Broadcom PHY losses the first recieved packet after SW/HW reset.
   This cause the ANT tests to fail (the tests get out of synchronize.
   
4. The driver supports only boards with 1 MII PHY only

5. The driver doesn't support boards that both SymScr and MII PHY on the
   same board

6. On boards with MII PHY, the driver performs the autosense algorithm 
   on MII PHY media only.


Tests:

The following tests were run successfully on version 03.10:

   - Correct compatible to LLI interface (LLItest from ANT)

   - ANT testing (ODT 3.0, ANT 3.2):
     Short tests:
         tcp
         nfs
         ipx
         ipxff
         ipxii
         osi
         lmu22
         tcp-ipx
         tcp-osi
         tcp-lmu
         ipx-osi
         sped
         ncard

     All tests that were run passed successfully.     



History
=======

Version 03.00
-------------

New features and modifications:

1. Update the counters according the LLI spec
2. Update clock's crtical section to be protocted from clock interrupts
3. Update setting the TX tthreshold and adapter serial speed when using the
   autosense algorithm.
4. Update loopback packets to be loopbacked to the upper layers without 
   the CRC.
5. Changes in space.c :
   
   XXX_UNIFORM_CARD_MODEL parameter was removed.


Limitations:

Following are the known limitations of version 02.10:

1. The driver supports up to 4 ports.
   Due to PCI BIOS limitations, the user must be very careful when 
   configuring multiple PCI boards. The chains are bound in the order 
   the BIOS finds the adapters on the PCI bus, therefore must make sure 
   that the chains are set correctly. This is particularly true for boards
   with PCI-PCI bridges, where the adapters are on a PCI bus with a bus
   number higher than zero and therefore are found by the PCI BIOS after
   all the devices on buses with lower numbers. 

   For example:

   In a system with two DS21x40-based PCI boards installed (A and B)
   two chains are created:

      sco_tcp->dce0
      sco_tcp->dce1

   Assuming the PCI BIOS finds board A before board B, dce0 will be bound to
   board A and dce1 to board B.

   Removing board A, or adding another board C (that will be found by the BIOS
   before A or B) will cause a shift in the bindings.

2. The driver support only boards that their SROM was programmed in the
   format of version 1.0 and the boards that their SROM was programmed in 
   the classic version (32 bytes of Ethernet address and checksum).



Tests:

The following tests were run successfully on version 02.01:

   - Correct compatible to LLI interface (LLItest from ANT)

   - ANT testing (ODT 3.0, ANT 3.2):
     Short tests:
         tcp
         nfs
         ipx
         ipxff
         ipxii
         osi
         lmu22
         tcp-ipx
         tcp-osi
         tcp-lmu
         ipx-osi
         sped
         ncard

     All tests that were run passed successfully.     


Version 02.01
-------------

New features and modifications:

1. The default PCI burst length size (XXX_BURST_LENGTH keyword in space.c)
   for DS21040 and DS21041 was set to 16 longwords.
   The default PCI burst length size (XXX_BURST_LENGTH keyword in space.c)
   for DS21140 was set to 32 longwords.
2. In case of DS21040 and DS21041 boards : During intialization the driver 
   checks for PCI burst size override. If detected and a new value is either 
   0 (unlimited burst size) or 32, the driver modifies this value to 16 
   longwords.
3. A new information regarding the LLI interface caused some changes in the 
   code to be LLI compatible (the llitest in ANT checks the LLI interface).
4. A bug was found in the code that handle the snooze mode. In last version
   (02.01) if the user asked the driver to work in snooze mode (by setting
   the XXX_SNOOZE_MODE keyword in space.c to XXX_TRUE), the driver actually
   moved to sleep mode. In this release this was fixed - if XXX_SNOOZE_MODE 
   keyword is set to XXX_TRUE, the board will be in snooze mode.
5. Correct the code that handle receive buffers pre-allocation. The driver
   will allocate receive buffers only when the system has the resources.
6. Update the counters according the LLI spec
7. Modified values in space.c :
   
   XXX_DEBUG will get the following values : XXX_LEVEL_0, XXX_LEVEL_1, 
   XXX_LEVEL_2, XXX_LEVEL_3. The levels controllers which error message
   will be print / not print. (see space.c)

   A new value was added to XXX_CACHE_ALIGNMENT : XXX_CACHE_DEFAULT.
   This value means that the value that will be set to the cache alignment 
   will be the same value that was set to the burst length.
   XXX_CACHE_ALIGNMENT default value was changed to XXX_CACHE_DEFAULT. 


   A new value was added to XXX_BURST_LENGTH : XXX_PBL_DEFAULT.
   This value means that for DS21040 and DS21041 the burst length value 
   will be 16 and for DS21140 the value will be 32.
   XXX_BURST_LENGTH default value was changed to XXX_PBL_DEFAULT. 
8. The EISA support was removed. This include the following change in 
   space.c :

   The keywords : XXX_PLX_DC21040_EISA_ID_VAL and XXX_PLX_DC21140_EISA_ID_VAL
   were removed from space.c
9. Correct the message that appear in boot time for DS21140 that works in
   autosense mode to print the media that was selected during boot time.
10. Correct the SROM's code to support only SROMs with version 1.0
11. A cosmetic changes were done in the code. The module that handle the init
    code was split to some smaller modules.
12. Change netconfig scripts to be incremental scripts. This means that when
    a user calls "netconfig" to install a new chain, he will see the strings 
    of the boards that were installed plus the next board that he can 
    installed. In previous kits, when the user called "netconfig" he saw
    the strings of all boards (the boards that were installed and the ALL
    boards that were not installed).


Limitations:

Following are the known limitations of version 02.10:

1. The driver supports up to 4 ports.
   Due to PCI BIOS limitations, the user must be very careful when 
   configuring multiple PCI boards. The chains are bound in the order 
   the BIOS finds the adapters on the PCI bus, therefore must make sure 
   that the chains are set correctly. This is particularly true for boards
   with PCI-PCI bridges, where the adapters are on a PCI bus with a bus
   number higher than zero and therefore are found by the PCI BIOS after
   all the devices on buses with lower numbers. 

   For example:

   In a system with two DS21x40-based PCI boards installed (A and B)
   two chains are created:

      sco_tcp->dce0
      sco_tcp->dce1

   Assuming the PCI BIOS finds board A before board B, dce0 will be bound to
   board A and dce1 to board B.

   Removing board A, or adding another board C (that will be found by the BIOS
   before A or B) will cause a shift in the bindings.

2. The driver support only boards that their SROM was programmed in the
   format of version 1.0 and the boards that their SROM was programmed in 
   the classic version (32 bytes of Ethernet address and checksum).



Tests:

The following tests were run successfully on version 02.01:

   - Correct compatible to LLI interface (LLItest from ANT)
   - Correct using incremntal netconfig scripts 
   - Correct printing the init message during driver init time.
   - Correct operation when board boot in snooze mode.
   
   - ANT testing (ODT 3.0, ANT 3.2):
     Short tests:
         tcp
         nfs
         ipx
         ipxff
         ipxii
         osi
         lmu22
         tcp-ipx
         tcp-osi
         tcp-lmu
         ipx-osi
         sped
         ncard

     All tests that were run passed successfully.     


Version 02.01
-------------

New features and modifications:

Version 2.01 is a maintenance update to version 2.00. There are
no functionality changes, only fixes to problems.

1. Correct several issues regarding DS21140 Dynamic Autosensing:

   - Don't switch media if no link is found, unless a default media
     is specified in the SROM. If none is specified and no link is found,
     stay in last media. Important for board implementations that have
     false transient link indications, to prevent toggling endlessly.

   - Set <SCR> bit when in 10Mb. If the bit is not set, 100Mb activity
     may not be identified and media won't switch even though it should.

   - Set correct tx threshold values after switching media. In ver. 2.00
     the tx threshold was left at the values of the first media found,
     even if the medium was switched. Important only if the threshold
     is changed (in space.c) from the defaults.

2. Correct usage of internal timer in DS21140 power-up autosensing.
   In ver. 2.00 timeouts may have been too short, not allowing correct
   media detection in some extreme cases.

3. Fix value written to CSR6 in DS21140 (bit 25 is now "must be one").
   If bit is not set to 1, it may affect compliance with the Ethernet spec, 
   in some extreme cases. This is now a requirment in the DS21140 spec.

4. Clearify some explanations in space.c, in particular regarding the GPR
   values.

5. Fix custom scripts to work correctly on OpenServer 5.0. The limitation
   of having to run netconfig before custom is now removed. Also,
   the system came up okay when no network cards were installed (removing
   the limitation detected in the beta version).

6. Removed an extra prompt to hit <return> in the custom init script.

7. Fix interrupt mask for DS21140. This change has no functional effect,
   it is a cosmetic change.

Limitations:

Following are the known limitations of version 02.01:

1. The driver supports up to 4 ports.
   Due to PCI BIOS limitations, the user must be very careful when 
   configuring multiple PCI boards. The chains are bound in the order 
   the BIOS finds the adapters on the PCI bus, therefore must make sure 
   that the chains are set correctly. This is particularly true for boards
   with PCI-PCI bridges, where the adapters are on a PCI bus with a bus
   number higher than zero and therefore are found by the PCI BIOS after
   all the devices on buses with lower numbers. 

   For example:

   In a system with two DS21x40-based PCI boards installed (A and B)
   two chains are created:

      sco_tcp->dce0
      sco_tcp->dce1

   Assuming the PCI BIOS finds board A before board B, dce0 will be bound to
   board A and dce1 to board B.

   Removing board A, or adding another board C (that will be found by the BIOS
   before A or B) will cause a shift in the bindings.

2. The driver support only boards that their SROM was programmed in the
   format of version 1.0 and the boards that their SROM was programmed in 
   the classic version (32 bytes of Ethernet address and checksum).



Tests:

The following tests were run successfully on version 02.01:
   - Correct dynamic autosensing of TP and SYM_SCR (TP 100Mb) on DS21140
     rev 1.2 based adapters.
   - Correct installation and operation of 1 and 2 adapters on SCO OpenServer.
   - ANT testing (ODT 3.0, ANT 3.2):
     Short tests:
         tcp
         nfs
         ipx
         ipxff
         ipxii
         osi
         lmu22
         tcp-ipx
         tcp-osi
         tcp-lmu

     All tests that were run passed successfully.     


Version 02.00
-------------

New features and modifications:

1. New naming convention: identifiers in space.c were changed from
   DCE_***** to XXX_*****.
   Also the identifiers in dce_space.h were changed.
   This is to make the decoupling between Digital Equipment and the
   board manufacturers easier.

2. Dynamic autosense for DS21041 based adapters is now supported. The
   driver will try to find a link on another port if the currently
   selected port loses its link. If the TP link is present, the driver
   will always select that port.

3. Startup and dynamic autosense is now supported for DS21140 based
   adapters. For rev 1.1 only startup autosense is supported, for rev
   1.2 and up also dynamic autosense is supported. The driver will try
   to use the medium with the highest precedence, as defined in the
   SROM.
   The default medium for DS21140 is now AUTOSENSE, not SYM_SCR as it
   was until now (see space.c).

4. SCO OpenServer 5.0 (Everest is now supported). The driver was successfully
   installed and run on an OpenServer system (including multiple board
   configurations).

   NOTE: when using the Software Manager to install the distribution kit,
   the system prints the message "device not found".
   This is NOT an error - the installation searches for the driver in
   the system before installing, to prevent problems. In ODT this search
   is silent, in Everest it is verbose. The fact that the device was not
   found is OKAY.

5. New keywords in space.c:

      XXX_SNOOZE_MODE
      For use in future devices. Currently has no effect.

      XXX_100MB_THRESHOLD
      Sets the Tx threshold value for DS21140 in 100Mb mode (SYM_SCR).
      The effects on the performance have not been measured yet, but the
      option is made available in this release.

6. Modified values in space.c :

      XXX_DC2104X_DEFAULT_SERIAL_MODE -> XXX_DC2104X_DEF_SERIAL_MODE 
      XXX_DC21140_DEFAULT_SERIAL_MODE -> XXX_DC21140_DEF_SERIAL_MODE 


Limitations:

Following are the known limitations of version 02.00:

1. The driver supports up to 4 ports.
   Due to PCI BIOS limitations, the user must be very careful when 
   configuring multiple PCI boards. The chains are bound in the order 
   the BIOS finds the adapters on the PCI bus, therefore must make sure 
   that the chains are set correctly. This is particularly true for boards
   with PCI-PCI bridges, where the adapters are on a PCI bus with a bus
   number higher than zero and therefore are found by the PCI BIOS after
   all the devices on buses with lower numbers. 

   For example:

   In a system with two DS21x40-based PCI boards installed (A and B)
   two chains are created:

      sco_tcp->dce0
      sco_tcp->dce1

   Assuming the PCI BIOS finds board A before board B, dce0 will be bound to
   board A and dce1 to board B.

   Removing board A, or adding another board C (that will be found by the BIOS
   before A or B) will cause a shift in the bindings.

2. The driver support only boards that their SROM was programmed in the
   format of version 1.0 and the boards that their SROM was programmed in 
   the classic version (32 bytes of Ethernet address and checksum).



4. IMPORTANT! On SCO OpenServer (Everest), before removing the driver using 
   the Software Manager, it must be removed using netconfig. Failing to do 
   so on one occasion CORRUPTED the system!
   This behaviour couldn't be reproduced, but until the issue is fully
   resolved it is good practice to use netconfig before the Software Manager.

5. In the beta versions of SCO OpenServer, if the networking is started
   and there is no board in the system, one of the system modules panicked
   (ksl.c, not the driver). This hasn't been checked yet in the final version.
   

Tests:

The following tests were run successfully on version 02.00:
   - Boot time detection of all media on DS21041 and DS21140 based
     adapters (TP, AUI, BNC, SYM_SCR (TP 100Mb)).
   - Correct dynamic autosensing of all media on DS21041 based adapters
     (TP, AUI, BNC).
   - Correct dynamic autosensing of TP and SYM_SCR (TP 100Mb) on DS21140
     rev 1.2 based adapters.
   - Correct installation and operation of 1 and 2 adapters on SCO OpenServer.
   - ANT testing (ODT 3.0, ANT 3.2):
     Short tests:
         tcp
         nfs
         ipx
         ipxff
         ipxii
         osi
         lmu22
         tcp-ipx
         tcp-osi
         tcp-lmu
         ipx-osi
         ipx-lmu
     Medium tests:
         tcp
         nfs
         ipx
         ipxff
         ipxii
         osi
         lmu22
         tcp-ipx
         tcp-osi
         ipx-osi
     Long tests:
         tcp
         nfs
         lmu22

     All tests that were run passed successfully.     


Version 01.03
-------------

New features and modifications:

1.  Fix bug when using GEP values that were given in space.c and are different
    from the values that were read from the SROM.

2.  Fix bug in initialize DS21041 to TP mode.

3.  Fix bug in initialize DS21041 to TP-link test disable mode.

4.  Fix bug in initialize DS21040 to TP-link test disable mode.

5.  Split the error message "[DCEinit] Could not initialize driver" to more
    specific error messages.

6.  Change the delay in the SROM.

7.  Fix bug in the XXXintr routine.

8.  Increase the critical area in the XXXintr routine.

9.  Due to bug - the location of calling the "add_intr_handler" routine
    was changed.

10. Add some driver specific counters.

11. Fix bug in the xxx_open routine - in the cases that the routine is failed.

12. Change the handling of the TX threhold value.

13. Change the default values of : burst length, TX threshold and cache
    alignment in space.c 

14. Fix bug in using the "printcfg" routine.

15. Fix bug in counters.

16. Fix bug in cases the transmit packet has number of segments > number
    of descriptors in the transmit list.

17. Fix bug in the transmit swiss cheese workaround.

18. Changes in space.c :

    Keywords that were removed :

    * DCE_BACK_PRESSURE
    * DCE_CAPTURE_EFFECT_ENABLE


    Keywords that there values/value-names were changed:
    
    * DCE_BURST_LENGTH. 
         Old value names : 0, 1, 2, 4, 8, 16, 32.
         New value names : DCE_PBL_0, DCE_PBL_1, DCE_PBL_2, DCE_PBL_4, 
                           DCE_PBL_8, DCE_PBL_16, DCE_PBL_32.
       

    * Keywords that their default values were changed :

      DCE_BURST_LENGTH : 16 -> DCE_PBL_32
      DCE_CACHE_ALIGNMENT : DCE_CACHE_16 -> DCE_CACHE_32
      DCE_10MB_THRESHOLD : DCE_10MB_THRESHOLD_160 -> DCE_10MB_THRESHOLD_96

    * Keywords that were deleted:

      DCE_PCI_DC21040_CFID_VAL
      DCE_PCI_DC21140_CFID_VAL
      DCE_PCI_DC21041_CFID_VAL


19. Change the default values for TP and TP-Full-duplex (the default values
    are used when the SROM is programing in the old format).



Limitations:

Following are the known limitations of version 01.03:

1. The driver supports up to 4 ports. 
   Due to PCI BIOS limitations, the user must be very careful when 
   configuring multiple PCI boards. The chains are bound in the order 
   the BIOS finds the adapters on the PCI bus, therefore must make sure 
   that the chains are set correctly. This is particularly true for boards
   with PCI-PCI bridges, where the adapters are on a PCI bus with a bus
   number higher than zero and therefore are found by the PCI BIOS after
   all the devices on buses with lower numbers. 

   For example:

   In a system with two DS21x40-based PCI boards installed (A and B)
   two chains are created:

      sco_tcp->dce0
      sco_tcp->dce1

   Assuming the PCI BIOS finds board A before board B, dce0 will be bound to
   board A and dce1 to board B.

   Removing board A, or adding another board C (that will be found by the BIOS
   before A or B) will cause a shift in the bindings.

2. The driver support only boards that their SROM was programmed in the
   format of version 1.0 and the boards that their SROM was programmed in 
   the classic version (32 bytes of Ethernet address and checksum).



Version 01.02
-------------

New features and modifications:

1.  Add some more error messages in the driver. Also change some of the old 
    error messages in the driver.

2.  Add support to DS21401.

3.  Add support to SROM version 1.0

4.  Add support to SROM that was programmed in the classic format: 
    32 bytes of Ethernet address and checksum.

5.  Change the TX and RX descriptors list : the descriptors addresses are
    32 bytes longword aligned.

6.  Fix bug in CSMA/CD receive packets : remove the padding of shorts
    packets when pushing them up in the stream.

7.  Fix bug when moving to promiscuous mode.

8.  Add workaround for PCMC revision 1 INTEL chipset - when working in cache
    mode write-back.

9.  Changes in space.c :

    Change in name:
    DCE_DC21040_SIA_MODE -> DCE_DC2104X_SIA_MODE

    New keyword:
    DCE_DC21041_CFID_VAL

    The values of DCE_DC2104X_SIA_MODE:
    DCE_TP_MODE             -> DCE_TP
    DCE_AUI_MODE            -> DCE_AUI
    DCE_BNC_MODE            -> DCE_BNC
    DCE_AUTODETECT_MODE     -> DCE_AUTOSENSE
    DCE_TP_FULL_DUPLEX_MODE -> DCE_TP_FULL_DUPLEX
    DCE_TP_IGNORE_LINKTEST_MODE_POS_MODE -> DCE_TP_LINK_DISABLE
    DCE_TP_IGNORE_LINKTEST_MODE_NEG_MODE -> DCE_TP_LINK_DISABLE
    new value : 
    DCE_DC2104X_DEFAULT_SERIAL_MODE

    The values of DCE_DC21140_SERIAL_MODE:
    DCE_10MB_MODE              -> DCE_TP
    DCE_10MB_FULL_DUPLEX_MODE  -> DCE_TP_FULL_DUPLEX
    DCE_100MB_MODE             -> DCE_SYM_SCR
    DCE_100MB_FULL_DUPLEX_MODE -> DCE_SYM_SCR_FULL_DUPLEX
    DCE_10MB_MODE -> DCE_TP
    new values : 
    DCE_BNC
    DCE_AUI
    DCE_DC21140_DEFAULT_SERIAL_MODE



Limitations:

Following are the known limitations of version 01.03:

1. No performance tuning has been done on the driver.

2. The driver supports up to 4 ports. 
   Due to PCI BIOS limitations, the user must be very careful when 
   configuring multiple PCI boards. The chains are bound in the order 
   the BIOS finds the adapters on the PCI bus, therefore must make sure 
   that the chains are set correctly. This is particularly true for boards
   with PCI-PCI bridges, where the adapters are on a PCI bus with a bus
   number higher than zero and therefore are found by the PCI BIOS after
   all the devices on buses with lower numbers. 

   For example:

   In a system with two DS21x40-based PCI boards installed (A and B)
   two chains are created:

      sco_tcp->dce0
      sco_tcp->dce1

   Assuming the PCI BIOS finds board A before board B, dce0 will be bound to
   board A and dce1 to board B.

   Removing board A, or adding another board C (that will be found by the BIOS
   before A or B) will cause a shift in the bindings.

3. The driver support only boards that their SROM was programmed in the
   format of version 1.0 and the boards that their SROM was programmed in 
   the classic version (32 bytes of Ethernet address and checksum).


5. It is recommended to use the default values for the variables : 
   "DCE_DC21140_GPR_CTRL" and "DCE_DC21140_GPR_DATA" in space.c (the default
   values are DCE_GPR_DEFAULT for DC21140_GPR_CTRL and DCE_GPR_DEFAULT for
   DC21140_GPR_DATA).
   The driver doesn't work with different values in this release.

6. It isn't recommended to use the mode DCE_TP_LINK_DISABLE for
   DCE_DC2104X_SIA_MODE (this variable can be found in space.c). This mode 
   may won't work for this release.

7. Back pressure :
   It isn't recommended to use this feature (by setting the DCE_BACK_PRESSURE
   variable in space.c to DCE_TRUE) since the DS2104x don't support
   this feature anymore.

8. Capture effect :
   It isn't recommended to use this feature (by setting the 
   DCE_CAPTURE_EFFECT_ENABLE variable in space.c to DCE_TRUE) since there
   is a bug in the DCEchip DS2104x that reduces the efficiency.

