More README updates, particularly in regard to DEC's Absolute Loader
This commit is contained in:
Jeff Parsons
Jeff Parsons
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ded8c1841d
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5d5629c27b
12 changed files with 97 additions and 52 deletions
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@ -7,8 +7,8 @@ permalink: /apps/pdp11/boot/bootstrap/
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DEC PDP-11 Bootstrap Loader
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---------------------------
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The **Bootstrap Loader** is a small program that loads the **[Absolute Loader](/apps/pdp11/tapes/absloader/)**,
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which is then used to load other PDP-11 tapes, such as **[BASIC (Single User)](/apps/pdp11/tabes/basic/)**.
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The **Bootstrap Loader** is a small program that loads the [Absolute Loader](/apps/pdp11/tapes/absloader/),
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which is then used to load other PDP-11 tapes, such as [BASIC (Single User)](/apps/pdp11/tabes/basic/).
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Here's what the **Bootstrap Loader** looks like:
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@ -15,14 +15,5 @@ We have archived the following DEC PDP-11 Tapes:
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along with a copy of the [DEC PDP-11 Bootstrap Loader](/apps/pdp11/boot/bootstrap/), which is required if you actually want
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to load any of the above tapes into memory using the [PC11 High-Speed Paper Tape Reader/Punch](/devices/pdp11/pc11/).
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To make it easy for PDPjs machines to load these tapes, we created the following High-Speed
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Paper Tape Reader (PC11) configurations:
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- [demo.xml](/devices/pdp11/pc11/demo.xml)
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which is typically instantiated by a Machine XML file using:
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<device ref="/devices/pdp11/pc11/demo.xml"/>
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These configuration files create UI controls that allow you to choose from a set of tapes that are automatically sent
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to the machine's PC11 device.
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For the most part, the tapes we have archived are in the DEC Absolute Loader format. More information about that format
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is on the [Absolute Loader](absloader/) page.
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@ -8,10 +8,48 @@ DEC PDP-11 Absolute Loader
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--------------------------
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The Absolute Loader is a special tape image that must be loaded in order to load *other* tapes
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which use the Absolute Loader format. To see the Absolute Loader in action, start with the
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[Bootstrap Loader Demo](/devices/pdp11/machine/1120/bootstrap/debugger/).
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that use what we'll call the "Absolute Format." To see the Absolute Loader in action, start with the
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[PDP-11/20 Bootstrap Loader Demo](/devices/pdp11/machine/1120/bootstrap/debugger/).
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PCjs has archived the following DEC resources:
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The *loadImage()* interface of the [PDPjs RAM Component](/modules/pdp11/lib/ram.js) explains what
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we know about the "Absolute Format":
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Data on tapes in the "Absolute Format" is organized into blocks; each block begins with
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a 6-byte header:
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2-byte signature (0x0001)
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2-byte block length (N + 6, because it includes the 6-byte header)
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2-byte load address
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followed by N data bytes. If N is zero, then the 2-byte load address is the exec address,
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unless the address is odd (usually 1). DEC's Absolute Loader jumps to the exec address
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in former case, halts in the latter.
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All values are stored "little endian" (low byte followed by high byte), just like the
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PDP-11's memory architecture.
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After the data bytes, there is a single checksum byte. The 8-bit sum of all the bytes in
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the block (including the header bytes and checksum byte) should be zero.
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ANOMALIES: Tape files don't always begin with a signature word, so I allow any number of
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leading zeros before the first signature. Tape files don't always end cleanly either, so as
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soon as I see an invalid signature, I break out of the loop without signalling an error, as
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long as at least ONE block was successfully processed. In fact, it's possible that as
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soon as a block with ZERO data bytes is encountered, processing is supposed to stop, but
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I haven't examined enough tapes (or the Absolute Loader code) to know for sure.
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[Other sites](http://www.retrocmp.com/stories/dec-pc05-papertape/242-dec-pc05-working-with-paper-tapes)
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have referred to this tape format as the "Standard Absolute" format, but I've not found confirmation of
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that terminology in any DEC publication. In fact, I think that term may have been a misreading of instructions
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found in DEC manuals like the ["MEM EXER 16K" Diagnostics Manual](http://archive.pcjs.org/pubs/dec/pdp11/other/AC-9045F-MC_CZQMCF0-0-124K-Mem-Exer-16k_Feb78.pdf):
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Load the program using any standard absolute loader.
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The most notable feature of the "Absolute Format" is that it contains no relocation information; it is
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designed for code that has been linked to run at a fixed ("absolute") address, or position-independent code
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for which a specific address has been selected, based on the amount of RAM present in the target machine.
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PCjs has archived the following Absolute Loader resources:
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- [Absolute Loader](DEC-11-L2PC-PO.json)
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- [LISTING OF PDP-11 ABSOLUTE LOADER (June 1975)](http://archive.pcjs.org/pubs/dec/pdp11/other/DEC-11-UABLA-A-LA_PDP-11AbsoluteLoaderListing_Jun75.pdf)
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@ -13,12 +13,12 @@ machines:
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DEC PDP-11 BASIC
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----------------
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The first PCjs machine to run DEC PDP-11 BASIC was this [PDP-11/20](/devices/pdp11/machine/1120/basic/debugger/),
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The first PDPjs machine to run DEC PDP-11 BASIC was this [PDP-11/20](/devices/pdp11/machine/1120/basic/debugger/),
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shown below.
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{% include machine.html id="test1120" %}
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PCjs has archived these DEC PDP-11 BASIC resources:
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PCjs has archived the following DEC PDP-11 BASIC resources:
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- [BASIC (Single User) Tape Image](DEC-11-AJPB-PB.json)
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- [LISTING OF BASIC/PTS (March 1974)](http://archive.pcjs.org/pubs/dec/pdp11/basic/AB-2045B-SC_BASIC_PTS_Listing_Mar77.pdf)
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@ -11,11 +11,11 @@ machines:
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PDP-11/20 BASIC Demo
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--------------------
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This machine pre-loads the **[DEC PDP-11 BASIC](/apps/pdp11/tapes/basic/)** tape image into 16Kb of RAM:
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This machine pre-loads the [DEC PDP-11 BASIC](/apps/pdp11/tapes/basic/) tape image into 16Kb of RAM:
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<ram id="ram" addr="0x0000" size="0x4000" file="/apps/pdp11/tapes/basic/DEC-11-AJPB-PB.json"/>
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You can also manually load it into memory using the **[Bootstrap Loader](/apps/pdp11/boot/bootstrap/)**.
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You can also manually load it into memory using the [Bootstrap Loader](/apps/pdp11/boot/bootstrap/).
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See the [Bootstrap Loader Demo](/devices/pdp11/machine/1120/bootstrap/) for details.
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{% include machine.html id="test1120" %}
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@ -12,11 +12,11 @@ machines:
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PDP-11/20 BASIC Demo (with Debugger)
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------------------------------------
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This machine pre-loads the **[DEC PDP-11 BASIC](/apps/pdp11/tapes/basic/)** tape image into 16Kb of RAM:
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This machine pre-loads the [DEC PDP-11 BASIC](/apps/pdp11/tapes/basic/) tape image into 16Kb of RAM:
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<ram id="ram" addr="0x0000" size="0x4000" file="/apps/pdp11/tapes/basic/DEC-11-AJPB-PB.json"/>
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You can also manually load it into memory using the **[Bootstrap Loader](/apps/pdp11/boot/bootstrap/)**.
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You can also manually load it into memory using the [Bootstrap Loader](/apps/pdp11/boot/bootstrap/).
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See the [Bootstrap Loader Demo (with Debugger)](/devices/pdp11/machine/1120/bootstrap/debugger/) for details.
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There are also some [Debugging Notes](/apps/pdp11/tapes/basic/#debugging-notes) on the
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@ -7,29 +7,29 @@ machines:
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type: pdp11
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---
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Bootstrap Loader Demo
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---------------------
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PDP-11/20 Bootstrap Loader Demo
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-------------------------------
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This machine pre-loads the **[Bootstrap Loader](/apps/pdp11/boot/bootstrap/)** code into 16Kb of RAM:
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This machine pre-loads the [Bootstrap Loader](/apps/pdp11/boot/bootstrap/) code into 16Kb of RAM:
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<ram id="ram" addr="0x0000" size="0x4000" file="/apps/pdp11/boot/bootstrap/BOOTSTRAP-16KB.json"/>
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and then pre-attaches the **[Absolute Loader](/apps/pdp11/tapes/absloader/)** tape image to the PC11 Paper Tape Reader:
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and then pre-attaches the [Absolute Loader](/apps/pdp11/tapes/absloader/) tape image to the PC11 Paper Tape Reader:
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<device id="pc11" type="pc11" baudReceive="9600" autoMount='{path:"/apps/pdp11/tapes/absloader/DEC-11-L2PC-PO.json"}' ...>...</device>
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Click "Run" to load the **[Absolute Loader](/apps/pdp11/tapes/absloader/)**.
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When the **[Bootstrap Loader](/apps/pdp11/boot/bootstrap/)** is finished, it will HALT,
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leaving the **[Absolute Loader](/apps/pdp11/tapes/absloader/)** ready to run immediately after the HALT.
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Click "Run" to load the [Absolute Loader](/apps/pdp11/tapes/absloader/).
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When the [Bootstrap Loader](/apps/pdp11/boot/bootstrap/) is finished, it will HALT,
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leaving the [Absolute Loader](/apps/pdp11/tapes/absloader/) ready to run immediately after the HALT.
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You can then select another tape image in the Absolute Loader format, such as **[BASIC (Single User)](/apps/pdp11/tapes/basic/)**,
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You can then select another tape image in the Absolute Loader format, such as [BASIC (Single User)](/apps/pdp11/tapes/basic/),
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click "Attach" and then "Run".
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If you need to start over, select "Bootstrap Loader (16Kb)" from the list of tapes and click "Load" instead of
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"Attach", re-installing the **[Bootstrap Loader](/apps/pdp11/boot/bootstrap/)** directly into RAM.
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"Attach", re-installing the [Bootstrap Loader](/apps/pdp11/boot/bootstrap/) directly into RAM.
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Alternatively, just press the "Reset" button. The RAM component was recently updated to restore pre-loaded images whenever
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the entire machine is reset. You'll still need to manually re-attach the **[Absolute Loader](/apps/pdp11/tapes/absloader/)**
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the entire machine is reset. You'll still need to manually re-attach the [Absolute Loader](/apps/pdp11/tapes/absloader/)
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tape image, however.
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{% include machine.html id="test1120" %}
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@ -8,29 +8,29 @@ machines:
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debugger: true
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---
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Bootstrap Loader Demo (with Debugger)
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-------------------------------------
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PDP-11/20 Bootstrap Loader Demo (with Debugger)
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-----------------------------------------------
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This machine pre-loads the **[Bootstrap Loader](/apps/pdp11/boot/bootstrap/)** code into 16Kb of RAM:
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This machine pre-loads the [Bootstrap Loader](/apps/pdp11/boot/bootstrap/) code into 16Kb of RAM:
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<ram id="ram" addr="0x0000" size="0x4000" file="/apps/pdp11/boot/bootstrap/BOOTSTRAP-16KB.json"/>
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and then pre-attaches the **[Absolute Loader](/apps/pdp11/tapes/absloader/)** tape image to the PC11 Paper Tape Reader:
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and then pre-attaches the [Absolute Loader](/apps/pdp11/tapes/absloader/) tape image to the PC11 Paper Tape Reader:
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<device id="pc11" type="pc11" baudReceive="9600" autoMount='{path:"/apps/pdp11/tapes/DEC-11-L2PC-PO.json"}' ...>...</device>
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Click "Run" to load the **[Absolute Loader](/apps/pdp11/tapes/absloader/)**.
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When the **[Bootstrap Loader](/apps/pdp11/boot/bootstrap/)** is finished, it will HALT,
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leaving the **[Absolute Loader](/apps/pdp11/tapes/absloader/)** ready to run immediately after the HALT.
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Click "Run" to load the [Absolute Loader](/apps/pdp11/tapes/absloader/).
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When the [Bootstrap Loader](/apps/pdp11/boot/bootstrap/) is finished, it will HALT,
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leaving the [Absolute Loader](/apps/pdp11/tapes/absloader/) ready to run immediately after the HALT.
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You can then select another tape image in the Absolute Loader format, such as **[BASIC (Single User)](/apps/pdp11/tapes/basic/)**,
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You can then select another tape image in the Absolute Loader format, such as [BASIC (Single User)](/apps/pdp11/tapes/basic/),
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click "Attach" and then "Run".
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If you need to start over, select "Bootstrap Loader (16Kb)" from the list of tapes and click "Load" instead of
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"Attach", re-installing the **[Bootstrap Loader](/apps/pdp11/boot/bootstrap/)** directly into RAM.
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"Attach", re-installing the [Bootstrap Loader](/apps/pdp11/boot/bootstrap/) directly into RAM.
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Alternatively, just press the "Reset" button. The RAM component was recently updated to restore pre-loaded images whenever
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the entire machine is reset. You'll still need to manually re-attach the **[Absolute Loader](/apps/pdp11/tapes/absloader/)**
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the entire machine is reset. You'll still need to manually re-attach the [Absolute Loader](/apps/pdp11/tapes/absloader/)
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tape image, however.
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{% include machine.html id="test1120" %}
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@ -7,10 +7,10 @@ machines:
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type: pdp11
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---
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Boot Test
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---------
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PDP-11/20 Boot Test
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-------------------
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This machine pre-loads the **[PDP-11 Boot Test](/apps/pdp11/boot/test/)** code into RAM:
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This machine pre-loads the [PDP-11 Boot Test](/apps/pdp11/boot/test/) code into RAM:
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<ram id="ram" addr="0x0000" size="0xE000" file="/apps/pdp11/boot/test/BOOTTEST.json" load="0xC000" exec="0xC000"/>
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@ -8,10 +8,10 @@ machines:
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debugger: true
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---
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Boot Test (with Debugger)
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-------------------------
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PDP-11/20 Boot Test (with Debugger)
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-----------------------------------
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This machine pre-loads the **[PDP-11 Boot Test](/apps/pdp11/boot/test/)** code into RAM:
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This machine pre-loads the [PDP-11 Boot Test](/apps/pdp11/boot/test/) code into RAM:
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<ram id="ram" addr="0x0000" size="0xE000" file="/apps/pdp11/boot/test/BOOTTEST.json" load="0xC000" exec="0xC000"/>
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@ -9,12 +9,24 @@ PC11 High-Speed Paper Tape Reader/Punch
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PDPjs implements the PC11 component in [pc11.js](/modules/pdp11/lib/pc11.js).
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A selection of [Paper Tape Images](/apps/pdp11/tapes/) have been archived for use by PDPjs machines:
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PDPjs machines that contain a PC11 Tape Reader include:
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- [Bootstrap Loader Demo](/devices/pdp11/machine/1120/bootstrap/)
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- [PDP-11/20 BASIC Demo](/devices/pdp11/machine/1120/basic/) (with [Debugger](/devices/pdp11/machine/1120/basic/debugger/))
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The tape images are typically listed in a common configuration file that all machines can use, such as [demo.xml](demo.xml):
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We have archived a selection of [Paper Tape Images](/apps/pdp11/tapes/) for use by those machines.
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To make it easy for PDPjs machines to load those tapes, we created the following High-Speed Paper Tape Reader (PC11)
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Device XML file:
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- [Demo](/devices/pdp11/pc11/demo.xml)
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which is typically referenced by a Machine XML file as:
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<device ref="/devices/pdp11/pc11/demo.xml"/>
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Device XML files typically configure the device, list all the resource the device will use, and define UI elements
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used to control the device, such as choosing which tape should be "attached" to the PC11 device. For example:
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<?xml version="1.0" encoding="UTF-8"?>
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<device id="pc11" type="pc11" baudReceive="9600" autoMount='{path:"/apps/pdp11/tapes/absloader/DEC-11-L2PC-PO.json"}' pos="left" width="35%" padLeft="8px" padBottom="8px">
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@ -249,6 +249,9 @@ RAMPDP11.prototype.reset = function()
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/**
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* loadImage(aBytes, addrLoad, addrExec, addrInit, fReset)
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*
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* If the array contains an image in the "Absolute Format," load it as specified by
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* the format; otherwise, load it as-is using the address(es) supplied.
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*
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* @this {RAMPDP11}
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* @param {Array|Uint8Array} aBytes
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* @param {number|null} [addrLoad]
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@ -261,14 +264,15 @@ RAMPDP11.prototype.loadImage = function(aBytes, addrLoad, addrExec, addrInit, fR
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{
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var fLoaded = false;
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/*
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* Data on tapes is organized into blocks; each block begins with a 6-byte header:
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* Data on tapes in the "Absolute Format" is organized into blocks; each block begins with
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* a 6-byte header:
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*
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* 2-byte signature (0x0001)
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* 2-byte block length (N + 6, because it includes the 6-byte header)
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* 2-byte load address
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*
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* followed by N data bytes. If N is zero, then the 2-byte load address is the exec address,
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* unless the address is odd (usually 1). DEC's "Absolute Loader" jumps to the exec address
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* unless the address is odd (usually 1). DEC's Absolute Loader jumps to the exec address
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* in former case, halts in the latter.
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*
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* All values are stored "little endian" (low byte followed by high byte), just like the
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