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Fix typo in dz11/dc speed botch: 19200 is actually 19800, not 19600. 

Explain more fully why DZ/dc devices lose as PPP/slip interfaces.
This commit is contained in:
jonathan 1998-02-23 19:46:24 +00:00
parent 5ad9218203
commit 4c9de2fb64
1 changed files with 48 additions and 29 deletions
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77
share/man/man4/man4.pmax/dc.4
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@ -27,21 +27,20 @@
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" $NetBSD: dc.4,v 1.2 1997/10/13 11:23:45 lukem Exp $
.\" $NetBSD: dc.4,v 1.3 1998/02/23 19:46:24 jonathan Exp $
.\"
.Dd August 6, 1996
.Dd February 20, 1998
.Dt DC 4 pmax
.Os NetBSD 1.2a
.Os NetBSD
.Sh NAME
.Nm dc
.Nd
dc659,dc7085 DZ11-on-a-chip serial communications interface
dc659, dc7085 DZ11-on-a-chip serial communications interface
.Sh SYNOPSIS
.Cd "dc0 at ioasic?"
.Cd "dc0 at mainbus"
.Cd "dc1 at mainbus"
.Cd "dc2 at mainbus"
.Cd "dc0 at vsbus"
.Sh DESCRIPTION
THe
.Nm
@ -64,34 +63,54 @@ baseboard devices on the Vaxstation 2000 and 3100.
.Pp
The
.Nm
device is essentially a single-chip clone of the DZ-11.
It has a small input silo shared across all input ports.
Model control lines are present on two of the four ports.
The device does not interrupt on modem transitions; instead,
device is in essence a single-chip clone of the DZ-11.
The DZ-11 hardware design severely constrains performance.
One small input silo is shared across all input ports.
The
.Nm dc
hardware does not interrupt on modem transitions; instead,
they are detected via polling.
Only two lines on a baseboard dc7085 have modem control signals; the
other two are wired for a keyboard and mouse.
On some implementations, only partial modem control (sufficent for
Unix dialup) is provided, while others provide full modem control.
Speeds greater than 19200 are not supported. The 19200 speed is rumoured
to actually be 19600, presumably for bug-compatibility with the DZ-11.
Only two lines on a baseboard
.Nm dc
device have any modem control signals;
the other two lines are wired for a keyboard and mouse.
On some implementations (e.g., Decstation 3100), the hardware does not
bring out modem flow-control signals to the bulkhead. Only modem
carrier transition are provided. This is adequate for Unix dialin
and dialout detection, but without hardware flow control, the
.Nm
device is prone to overruns when used for serial-line protocols.
The Decstation 5000/200
.Nm
hardware provides full modem control on
both bulkhead RS-232 ports and is less prone to overrun.
.Sh BUGS
.Pp
The 19200 speed on all
.Nm
devices is actually implemented as 19800,
presumably for bug-compatibility with the original DZ-11.
This is a hardware feature and cannot be corrected in software.
Many serial devices at 19200 fail to interoperate with the
.Nm
at its 19800 speed setting.
.Pp
The Decstation 5000/200 can set a bit in the system register
to allow the
.Nm
to run at 38400, but this applies to all four lines and disables
the 19200 speed on all four lines. This feature is not currently supported.
.Pp
The
.Nm
driver should be merged into a single driver supporting the original
DZ-11, DZ-32, and Qbus DZV-11 and DZQ-11 clones.
.Sh HISTORY
The
.Nm
driver
first appeared in
.Bx 4.4 /pmax. Support for Vax implementations is
.Ud .
.Sh BUGS
The Decstation 5000 can set a bit in the system register
to allow the
.Nm
to run at 38400, but this applies to all four lines and disables
the 19200 speed. This feature is not currently supported.
.Pp
The driver should probably support the original DZ-11, DZ-32,
and Qbus DZV-11 and DZQ-11 clones.
.Bx 4.4 /pmax. This manual page first appeared in
.Nx 1.2 .