B10.3.2 The RECEIVE CONTROL BLOCKb

To receive data, a receive control block must be set up.  Its format
follows:


BBC Microcomputer			ATOM and Systems

0  ------------------------- 		0  -------------------------
   |  Receive block number |              |         Flag          |
   |    (initially &00)    |		   |                       |
1  |-----------------------|		1  |-----------------------|
   |         Flag          |		   |      Port number      |
   |                       |		   |                       |
2  |-----------------------|		2  |-----------------------|
   |      Port number      |		   |  Station number (lo)  |
   |                       |		   |                       |
3  |-----------------------|		3  |-----------------------|
   |  Station number (lo)  |		   |  Station number (hi)  |
   |                       |		   |                       |
4  |-----------------------|		4  |-----------------------|
   |  Station number (hi)  |		   | Pointer to Buffer (lo)|
   |                       |		   |                       |
5  |-----------------------|		5  |        -------        |
   | Pointer to Buffer (0) |		   | Pointer to Buffer (hi)|
   |                       |		   |                       |
6  |        -------        |		6  |-----------------------|
   | Pointer to Buffer (1) |		   |        Pointer        |
   |                       |		   |   to Buffer end (lo)  |
7  |        -------        |		7  |        -------        |
   | Pointer to Buffer (2) |		   |        Pointer        |
   |                       |		   |   to Buffer end (hi)  |
8  |        -------        |		8  |-----------------------|
   | Pointer to Buffer (3) |
   |                       |
9  |-----------------------|
   |        Pointer        |
   |   to Buffer end (0)   |
10 |        -------        |
   |        Pointer        |
   |   to Buffer end (1)   |
11 |        -------        |
   |        Pointer        |
   |   to Buffer end (2)   |
12 |        -------        |
   |        Pointer        |
   |   to Buffer end (3)   |
13 |-----------------------|

The RECEIVE BLOCK NUMBER should be &00 on entry.  On exit, it will be set
to the control block number, or &00 if the block was unable to be opened
because the space limit was reached.  On the ATOM and SYSTEMS the program
has to interrogate the network system to see if a reception has happened. 

The FLAG byte indicates the state of the RXCB.  It should initially be set
to &7F to indicate readiness to receive, it will be altered on reception
(see 10.3.4).

The STATION number indicates what station the control block will accept
messages from.  If this is 0, it will accept messages from any station
(but only on the specified port).

The PORT number indicates on which port messages will be accepted.  A port
number of 0 indicates any port.

									77
Both the station number and port can be zero, and the station will then
accept any message which is addressed to it from any station on any port.



B10.3.3 The Receive Control Block After Receptionb

After a message is received, the following changes will occur to fields in
the control block which accepted the message:

	1) The top bit of the flag byte is set.  The rest of the byte
	contains the control code sent from byte 0 of the corresponding
	transmit control block.

	2) The station number, if originally zero, is modified to indicate
	which station actually sent the received message.

	3) The port number, if originally zero, is modified to indicate the
	port of the received message.

	4) The Buffer End pointer is modified to point to the end of the
	message in the buffer, if the message length is shorter than the
	bufferlength.  Notethat messages longer then the buffer length
	will not be accepted.

	The 'end of the message' is the byte after the last byte of the
	message.



B10.4 Broadcastb

If a station sets up a suitable control block, as given below, the data
within the block can be received by ANY BBC Machine with a suitable
receive block set up (the broadcast facility is not available for ATOM and
SYSTEM computers).  The recive block must be set up to listen to station
&FF or station &00 and the correct port (or port 0).  The TRANSMIT control
block for broadcast is:

		0  -----------------------------
		   |           Flag            |
		1  |---------------------------|
		   |        Port number        |
		2  |---------------------------|
		   |            &FF            |
		3  |---------------------------|
		   |            &FF            |
		4  |---------------------------|
		   |    eight bytes of data    |
		   |                           |
		   |---------------------------|














78
B10.5.6 MACHINE TYPEb

This primitive is designed to give some indication of the type of another
machine on the network.  It is effectively a peek of a store area which
has been set by the low-level software in the distant machine.

In all machines, this is set to be in the ECONET EPROM, and consists of
the following:

		   +--------------------------+
		   | Machine type number (lo) |
		   +         --------         +
		   | Machine type number (hi) |
		   +--------------------------|
		   | Software release no. (lo)|
		   +         --------         +
		   | Software release no. (hi)|
		   +--------------------------+


The machine type numbers and corresponding strings are:

     Type number	Machine
	   0		Reserved
	   1		BBC Microcomputer
	   2		ATOM
	   3		System 3 or 4
	   4		System 5
	   5		Master 128
	   6		Electron
	   7		Archimedes
	   8		(Reserved)
	   9		Acorn Communicator
	  10		Master ET
	  11		Acorn Filestore
	  12		Master Compact
	  13		IBM PC with Acorn EcoLink card
	  14		RISCiX Workstation
	  15
	  16
	   :
	   :
	   :
	&FFF8
	&FFF9
	&FFFA		SJ SCSI Interface
	&FFFB		IBM PC with SJ Econet card
	&FFFC		Nascom-2
	&FFFD		Research Machines 480Z
	&FFFE		SJ Research Fileserver
	&FFFF		Research machines 380Z or CP/M














									85
Control block:

BBC Microcomputer			ATOM and Systems


0  -------------------------		0  -------------------------
   |      Flag = &88       |		   |      Flag = &88       |
   |                       |		   |                       |
1  |-----------------------|		1  |-----------------------|
   |         Zero          |		   |         Zero          |
   |                       |		   |                       |
2  |-----------------------|		2  |-----------------------|
   |  Station number (lo)  |		   |  Station number (lo)  |
   |                       |		   |                       |
3  |-----------------------|		3  |-----------------------|
   |  Station number (hi)  |		   |  Station number (hi)  |
   |                       |		   |                       |
4  |-----------------------|		4  |-----------------------|
   |   Pointer to BUFFER   |		   |   Pointer to BUFFER   |
   |  in local machine (0) |		   |  in local machine (lo)|
5  |        -------        |		5  |        -------        |
   |   Pointer to BUFFER   |		   |   Pointer to BUFFER   |
   |  in local machine (1) |		   |  in local machine (hi)|
6  |        -------        |		6  |-----------------------|
   |   Pointer to BUFFER   |		   |        Pointer        |
   |  in local machine (2) |		   |   to Buffer end (lo)  |
7  |        -------        |		7  |        -------        |
   |   Pointer to BUFFER   |		   |        Pointer        |
   |  in local machine (3) |		   |   to Buffer end (hi)  |
8  |-----------------------|		8  |-----------------------|
   |        Pointer        |
   |   to Buffer end (0)   |
9  |        -------        |
   |        Pointer        |
   |   to Buffer end (1)   |
10 |        -------        |
   |        Pointer        |
   |   to Buffer end (2)   |
11 |        -------        |
   |        Pointer        |
   |   to Buffer end (3)   |
12 |-----------------------|























86
B10.5.9 Read Registersb

This operation reads the ARM registers in an Archimedes to the block of
memory in the local machine.  The call only works between Archimedes
computers.

The primitive has a control flag of &89.

The data read back is 20 4-byte words, each of which has an ARM register, in
the following order:


		0  +-------------+
		   |     R0      |
		4  +-------------+
		   |     R1      |
		8  +-------------+
		   |     R2      |
		12 +-------------+
		   |     R3      |
		16 +-------------+ 
		   |     R4      |
		20 +-------------+
		   |     R5      |
		24 +-------------+
		   |     R6      |
		28 +-------------+
		   |     R7      |
		32 +-------------+
		   |     R8      |
		36 +-------------+
		   |     R9      |
		40 +-------------+
		   |     R10     |
		44 +-------------+
		   |     R11     |
		48 +-------------+
		   |     R12     |
		52 +-------------+
		   |     R13     |
		56 +-------------+
		   |     R14     |
		60 +-------------+
		   |   PC (R15)  |
		64 +-------------+
		   |   R13_irg   |
		68 +-------------+
		   |   R14_irg   |
		72 +-------------+
		   |   R13_svc   |
		76 +-------------+
		   |   R14_svc   |
		80 +-------------+












									86a
Control block:

0  -------------------------
   |      Flag=&89         |
   |                       |
1  |-----------------------|
   |         Zero          |
   |                       |
2  |-----------------------|
   |  Station number (lo)  |
   |                       |
3  |-----------------------|
   |  Station number (hi)  |
   |                       |
4  |-----------------------|
   |   Pointer to BUFFER   |
   |  in local machine (0) |
5  |        --------       |
   |   Pointer to BUFFER   |
   |  in local machine (1) |
6  |        --------       |
   |   Pointer to BUFFER   |
   |  in local machine (2) |
7  |        --------       |
   |   Pointer to BUFFER   |
   |  in local machine (3) |
8  |-----------------------|
   |        Pointer        |
   |   to Buffer end (0)   |
9  |        --------       |
   |        Pointer        |
   |   to Buffer end (1)   |
10 |        --------       |
   |        Pointer        |
   |   to Buffer end (2)   |
11 |        --------       |
   |        Pointer        |
   |   to Buffer end (3)   |
12 |-----------------------|


























86b
B13.9.13 Read disk info - code 14b

1/ Client -> File server (command port)

     Bytes  1-5 = Standard TX header
     Byte   6   = first drive number to get info on
     Byte   7   = number of drives to get info on

2/ File server -> Client (reply port)

     Bytes  1-2 = Standard RX header
     Byte   3   = number of drives found
     Byte   4   = Drive number of first drive requested
     Bytes  5-20= Disk name on drive padded with spaces
     Byte  21   = Drive dumber of second drive requested
     Bytes 22-37= Disk name on second drive
     Bytes 38+  = Info on remaining drives in same format

Generally only two drives are present, but the interface will cope with
any number.

B13.9.14 Read logged on users - code 15b

1/ Client -> File server (command port)

     Bytes  1-5 = Standard TX header
     Byte   6   = First user entry to get info on
     Byte   7   = number of user entries to examine

2/ File server -> Client (reply port)

     Bytes  1-2 = Standard RX header
     Byte   3   = number of users found
     Bytes  4-5 = machine number where user logged on (lo then hi)
     Bytes  6+xx= User id. terminated by CR
     Byte  yy   = privilege of user - 0 unprivileged, non-0 privileged 
     Bytes zz+  = Further entries in same format

Note that the number of users found will be zero if the first user entry
to be examined is greater than the number of users logged on.  Also, some
file servers only list unprivileged users if the client is also an
unprivileged user. 

B13.9.15 Read date and time - code 16b

1/ Client -> File server (command port)

     Bytes  1-5 = Standard TX header

2/ File server -> Client (reply port)

     Bytes  1-2 = Standard RX header
     Bytes  3-4 = Date, standard format:
		  byte 3 (lo 5 bits) = day
		  byte 3 (hi 3 bits) = (year since 1982) DIV 16
		  byte 4 (lo 4 bits) = month
		  byte 4 (hi 4 bits) = year since 1981
     Bytes  5-7 = 0 or >59 if no time-board attached to file server
		  byte 5 - hours
		  byte 6 - minutes
		  byte 7 - seconds




110
B13.9.22 Log-off - code 23b

1/ Client -> File server (command port)

     Bytes  1-5 = Standard TX header

2/ File server -> Client (reply port)

     Bytes  1-2 = Standard RX header


B13.9.23 Read user info - code 24b

1/ Client -> File server (command port)

     Bytes  1-5 = Standard TX header
     Bytes  6+  = User name, terminated by CR

2/ Filer server -> Client (reply port) 

     Bytes  1-2 = Standard RX header
     Byte     3 = User privilege (0 - unprivileged, non-0 - privileged)
     Bytes  4-5 = Machine number logged on (lo byte first)

An error will be returned if the user is not logged on.

B13.9.24 Read File Server version number - code 25b

1/ Client -> File server (command port)

     Bytes  1-5 = Standard TX header

2/ File server -> Client (reply port)

     Bytes  1-2 = Standard RX header
     Bytes   3+ = Character string descibing version, terminated by CR.

B13.9.25 Read File Server Free Space - code 26b

1/ Client -> File server (command port)

     Bytes  1-5 = Standard TX header
     Bytes   6+ = Disk name, terminated by CR

2/ File server -> Client (reply port)

     Bytes  1-2 = Standard RX header
     Bytes  3-5 = Number of free blocks on disk

An error will be returned if the disk is not present.

B13.9.26 Create a directory - code 27b

1/ Client -> File server (command port)

     Bytes  1-5 = Standard TX header
     Bytes   6+ = Directory name, terminated by CR

2/ File server -> Client (reply port)

     Bytes  1-2 = Standard RX header




									113
B10.5.5 Remote Procedure Callb

This primitive allows remote procedure calls to be made in a remote
machine.  A procedure is identified by a 16 bit number and is completely
independant of the program counter.

In the BBC Machine, the mechanism for reading the arguments to the call is
the same as for REMOTE JSR.

An OPERATING SYSTEM PROCEDURE CALL primitive is provided with an identical
control block to the procedure call.  This primitive has a control flag of
&85.  This should not be used by ordinary users, and is called by other
routines.