rfc909.txt
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RFC-909 July 1984
Short Format - Format bit is SHORT=1
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-------------------------------+
|1| Mode | Mode Argument |
+-------------------------------+ +-+
| (31-16) | |
+---- Offset ---+ | Offset
| (15-0) | |
+-------------------------------+ +-+
Short Address Format
Figure 11
SHORT ADDRESS FIELDS:
Mode
The high-order bit is 1, indicating the short address
format. A list of the address modes supported is given
below. The interpretation of the remaining fields is as
described above for the long addressing format.
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LDP Specification Commands and Formats
Mode | Symbol | Address space
-----+--------------------+---------------------------
0 HOST Host
1 PHYS_MACRO Macro-memory
2 PHYS_MICRO Micro-memory
3 PHYS_I/O I/O space
4 PHYS_MACRO_PTR Macro contains a pointer
5 PHYS_REG Register
6 PHYS_REG_OFFSET Register plus offset
7 PHYS_REG_INDIRECT Register contains address
of a pointer
8 -
32 <reserved>
Short Address Modes
Figure 12
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RFC-909 July 1984
Page 28
LDP Specification Protocol Commands
CHAPTER 5
Protocol Commands
Protocol commands are used for error handling, for
synchronizing the command sequence number, and for communicating
protocol implementation parameters. Every protocol command has a
corresponding reply. All protocol commands are sent from the
host to the target, with replies flowing in the opposite
direction.
5.1 HELLO Command
The HELLO command is sent by the host to signal the start of
an LDP session. The target responds with HELLO_REPLY.
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 4 |
+---------------+---------------+
1 | PROTOCOL | HELLO |
+---------------+---------------+
HELLO Command Format
Figure 13
5.2 HELLO_REPLY
A HELLO_REPLY is sent by the target in response to the HELLO
command at the start of an LDP session. This reply is used to
inform the host about the target's implementation of LDP.
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RFC-909 July 1984
0 0 0 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---------------+---------------+
0 | 10 |
+---------------+---------------+
1 | PROTOCOL | HELLO_REPLY |
+---------------+---------------+
2 | LDP Version | System Type |
+---------------+---------------+
3 | Options |W|S| Implementation|
+---------------+---------------+
4 | Address Code | Reserved |
+---------------+---------------+
HELLO_REPLY Format
Figure 14
HELLO_REPLY FIELDS:
LDP Version
The target's LDP protocol version. If the current
host protocol version does not agree with the target's
protocol version, the host may terminate the session, or
may continue it, at the discretion of the implementor. The
current version number is 2.
System Type
The type of system running on the target. This is used as a
check against what the host thinks the target is. The host
is expected to have a table of target system types with
information about target address spaces, target-specific
commands and addressing modes, and so forth.
Currently defined system types are shown in Figure 15. This
list includes some systems normally thought of as 'hosts'
(e.g. C70, VAX), for implementations where targets actively
initiate and direct a load of themselves.
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LDP Specification Protocol Commands
Code | System | Description
--------+---------------+---------------------------
1 C30_16_BIT BBN 16-bit C30
2 C30_20_BIT BBN 20-bit C30
3 H316 Honeywell-316
4 BUTTERFLY BBN Butterfly
5 PDP-11 DEC PDP-11
6 C10 BBN C10
7 C50 BBN C50
8 PLURIBUS BBN Pluribus
9 C70 BBN C70
10 VAX DEC VAX
11 MACINTOSH Apple MacIntosh
System Types
Figure 15
Address Code
The address code indicates which LDP address format(s) the
target is prepared to use. Address codes are show in Figure
16.
Address Code | Symbol | Description
--------------+---------------+-----------------------------
1 LONG_ADDRESS Five word address format.
Supports all address modes
and commands.
2 SHORT_ADDRESS Three word address format.
Supports only physical and
host address modes. Only
the LOADER_DUMPER set of
commands are supported.
Target Address Codes
Figure 16
Implementation
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RFC-909 July 1984
The implementation level specifies which features of
the protocol are implemented in the target. There are
three levels of protocol implementation. These levels are
intended to correspond to the three most likely applications
of LDP: simple loading and dumping, basic debugging, and
full debugging. (Please see Implementations, above, for a
detailed description of implementation levels.) There are
are also several optional features that are not included in
any particular level.
Implementation levels are cumulative, that is, each higher
level includes the features of all previous levels. The
levels are shown in Figure 17.
Feature Level | Symbol | Description
--------------+---------------+-----------------------------
1 LOADER_DUMPER Loader/dumper subset of LDP
2 BASIC_DEBUGGER Control commands, CREATE
3 FULL_DEBUGGER FSM breakpoints
Feature Levels
Figure 17
Options
The options field (see Figure 18) is an eight-bit flag
field. Bit flags are used to indicate if the target has
implemented particular optional commands. Not all optional
commands are referenced in this field. Commands whose
implementation depends on target machine features are
omitted. The LDP application is expected to 'know' about
target features that are not intrinsic to the protocol.
Examples of target-dependent commands are commands that
refer to named objects (CREATE, LIST_NAMES).
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LDP Specification Protocol Commands
Mask | Symbol | Description
------+-------------+---------------+-----------------
1 STEP The STEP command is implemented
2 WATCHPOINTS Watchpoints are implemented
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