Difference between revisions of "DC11 asynchronous serial line interface"

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(Other DF11s too)
(Addesses, power, etc)
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The '''DC11 asynchronous serial line interface''' is an early [[UNIBUS]] [[peripheral]] which provides an [[asynchronous serial line]] connection to a [[modem]] (Bell 103 and 202 models), using an [[EIA RS-232 serial line interface|EIA RS-232]] interface. Both input and output used [[programmed I/O]] (with separate receive and transmit [[interrupt]]s).
+
The '''DC11 asynchronous serial line interface''' is an early [[UNIBUS]] [[peripheral]] which provides an [[asynchronous serial line]] connection to a [[modem]] (Bell 103 and 202 models), using an [[EIA RS-232 serial line interface|EIA RS-232]] interface. Both input and output used [[programmed I/O]] (with separate receive and transmit [[interrupt]]s); there was no [[buffer]]ing.
  
 
The line parameters:
 
The line parameters:
  
* baud rates (4 speeds, ranging from 50 to 1800, depending on the clock module)
+
* [[baud rate]]s (4 speeds, separate for transmit and receive, ranging from 50 to 1800, depending on the clock module )
 
* character length (5-8 bits)
 
* character length (5-8 bits)
 +
* output stop bits (1 or 2)
 
* input parity (even or odd)
 
* input parity (even or odd)
  
could be set under program control. A 'break' condition on the line (i.e. continuous assertion) could also be generated and detected. The speeds available with various models were:
+
could be set under program control. A 'break' condition on the line (i.e. continuous assertion) could also be generated and detected.
 +
 
 +
The speeds available with various models were:
  
 
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|}
 
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Other [[DF11 Communications Line Adapter]]s could be used to interface to other serial line types.
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Other [[DF11 Communications Line Adapter]]s could be used in place of the EIA RS-232 interface card.
  
 
==Device registers==
 
==Device registers==
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|Transmit Buffer Register      || DCTBUF || 774006
 
|Transmit Buffer Register      || DCTBUF || 774006
 
|}
 
|}
 +
 +
The [[address]]es shown are for the first DC11 in a system; additional ones (up to 32 total) are normally set to be at 774010, 774020, etc to 774370.
  
 
==Implementation==
 
==Implementation==
  
The implementation used a single custom [[system unit]] [[backplane]], containing two indepent DC11's, each consisting of:
+
The implementation used a single custom [[system unit]] [[backplane]], containing two independent DC11's, each consisting of:
  
 
* M794 Interface ([[DEC card form factor|quad]])
 
* M794 Interface ([[DEC card form factor|quad]])
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| 2 || G8000 filter || M454 clock || colspan="4" style="text-align:center;" | M794
 
| 2 || G8000 filter || M454 clock || colspan="4" style="text-align:center;" | M794
 
|-
 
|-
| 3 || power|| @ || colspan="4" style="text-align:center;" | M794
+
| 3 || Power|| @ || colspan="4" style="text-align:center;" | M794
 
|-
 
|-
 
| 4 || colspan="2" style="text-align:center;" | UNIBUS Out || M957 || M594 || M7821|| M105
 
| 4 || colspan="2" style="text-align:center;" | UNIBUS Out || M957 || M594 || M7821|| M105
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@ = M205 for -AD, -AE; M405 for -AX; or blank
 
@ = M205 for -AD, -AE; M405 for -AX; or blank
 +
 +
Power comes in on a single-width stub card in the A3 slot (as is canonical in the [[PDP-11/20]] generation of [[PDP-11]]s).
  
 
[[Category: UNIBUS Serial Interfaces]]
 
[[Category: UNIBUS Serial Interfaces]]

Revision as of 14:36, 29 September 2019

The DC11 asynchronous serial line interface is an early UNIBUS peripheral which provides an asynchronous serial line connection to a modem (Bell 103 and 202 models), using an EIA RS-232 interface. Both input and output used programmed I/O (with separate receive and transmit interrupts); there was no buffering.

The line parameters:

  • baud rates (4 speeds, separate for transmit and receive, ranging from 50 to 1800, depending on the clock module )
  • character length (5-8 bits)
  • output stop bits (1 or 2)
  • input parity (even or odd)

could be set under program control. A 'break' condition on the line (i.e. continuous assertion) could also be generated and detected.

The speeds available with various models were:

Model Speeds
-AA 300, 150, 134.5, 110
-AB 1800, 1200, 300, 110
-AC 1200, 600, 150, 110
-AD 150, 134.5, 110, 50
-AE 150, 134.5, 110, 75
-AG 1200, 300, 150, 134.5
-AH 1800, 1200, 134.5, 110
-AX Other (up to 19.6K), 150, 134.5, 110

Other DF11 Communications Line Adapters could be used in place of the EIA RS-232 interface card.

Device registers

Register Abbreviation Address
Receive Status Register DCRCSR 774000
Receive Buffer Regist DCRBUF 774002
Transmit Status Register DCTCSR 774004
Transmit Buffer Register DCTBUF 774006

The addresses shown are for the first DC11 in a system; additional ones (up to 32 total) are normally set to be at 774010, 774020, etc to 774370.

Implementation

The implementation used a single custom system unit backplane, containing two independent DC11's, each consisting of:

  • M794 Interface (quad)
  • M7821 - Interrupt control
  • M105 - Address selection
  • M594 EIA level converter
  • M957 data set cable connector

Board locations (as seen from the board insertion side of the backplane, not the wire-wrap pin side, as is common in DEC documentation) are:

Connector
Slot A B C D E F
1 UNIBUS In M957 M594 M7821 M105
2 G8000 filter M454 clock M794
3 Power @ M794
4 UNIBUS Out M957 M594 M7821 M105

@ = M205 for -AD, -AE; M405 for -AX; or blank

Power comes in on a single-width stub card in the A3 slot (as is canonical in the PDP-11/20 generation of PDP-11s).