27-Apr-84
							John Elkins
							ML3-2/E4l
 							DTN 223-6646




    			 Command Strings, Date and Time
    			 With the DECmate Master Menu



	This note  describes  the  technique  for  the  operating  system
	programmer  to  get  the  command  string, date and time from the
	Master Menu.

	When Master Menu transfers control to  an  operating  system,  it
	places  a  command  string  at a designated place in 6120 memory.
	The command string has the following format (character  positions
	are decimal offsets).


	Format of Command String
	________________________

		0..6	    id string;  this is one of the following:
			    COS_cmd
			    CPM_cmd
			    OS8_cmd
			    WPS_cmd
			    DOS_cmd

		7..7	    null

 		8..8	    binary length of the following command text

		9..88	    up to 80 characters of text to be interpreted
			    by the operating system as commands typed in

		89..89	    null

		90..97	    date:  in the format mm/dd/yy

		98..98	    null

		99..99	    			???

		100..100    Master Menu version number

		101..109    day-of-week:
			    Sunday
			    Monday
			    Tuesday
			    Wednesday
			    Thursday
			    Friday
			    Saturday
								   Page 2

		110..110    null
	
		111..118    time-of-day in the form hh:mm:ss.  This is  a
			    24 hour clock.

		119..119    time-of day, clock low

		120..120    time-of day, clock high
		
		121..121    date format:
			    0 =	invalid
			    1 = mm/dd/yy
			    2 = yy/mm/dd
			    3 = dd/mm/yy

		122..122    null


	NOTE: If the command id string contents is  not  appropriate  for
	the  operating  system being booted, the command string should be
	ignored by the operating system.

	Location of Master Menu Command String
	______________________________________

	The command string is placed at a  location  in  memory  depending
	upon  the  operating  system  being booted.  This has not changed
	since the original  description  that  appeared  in  the  printed
	documentation.

			CPM/80:		077600
			WPS:		167600
			C0S310:		167600
			MSDOS:		077600
			OS278:		077600

	NOTE: the high-order address bit indicates panel or  application
	memory:  O = application:  1 = panel.


	Getting The Current Time from Memory
	____________________________________

	This  is  documented  only  for   completeness.   Normally,   the
	operating  system  would have received the date and time from the
	Master Menu and then maintain  it  internally  rather  than  make
	access to the slushware maintained clock/calendar.

	Slushware is responsible for updating a  2-word  memory  location
	every  1/60 seconds.  Slushware adds 1 to this 'clock' every 1/60
	seconds.  Since the clock has 24  bits,  it  has  a  capacity  of
	2**24/60 seconds.  This comes out to something like 3.24 days.  A
	double-word value of 1 indicates 1/60 seconds past  midnight  and
	so forth.

	When Master Menu is activated, it accepts  the  time-of-day  from
	the  user  at  the  keyboard.  It  then  translates  this into an
	appropriate double-word number to place in the clock.
								   Page 3

	Here is the format of the clock/calendar:

		0:0		clock-low
		1:1		clock-high
		2:2[0:6]	binary month (1..12)
		2:2[7:12]	binary day of month (1..1)
		3:3[0:2]	binary day-of-week (l..7)
				(Sunday = 1 ... Saturday =7)
		3:3[3:11]	binary year-of-century (00..99)


	These data are found in	memory as follows.  Panel memory location
	4.5  in  field 0 contains the address of the CPODT table.  Offset
	66.67 (octal) of the CPODT table  contains  the  address  of  the
	clock/calendar.

	NOTE:  Pointers in panel memory consist of two words.  The  first
	word  contains  the 12-bit address.  The second word contains the
	6-bit field (00, 10, 20, 30, 40, 50, 60, 70).  The field value is
	in  the  appropriate form to use when using PRQs to peek at panel
	memory.

	Thus, the following code would move the clock/calendar to a place
	in user memory:

								   Page 4

	CLKCAL, ZBLOCK 4
	TABADR,	0 ; 0
	CLKADR, 0 ; 0

		.
		.
		.

		PR3
		5000+<0^10>+0	/PANEL FIELD 0
				/USER FIELD 0
		4		/MOVE FROM HERE IN PANEL MEMORY
		TABADR		/MOVE TO HERE IN USER MEMORY
		-2		/MINUS #WORDS TO TRANSFER
		-1		/TERMINATOR

		/ NOW, ADDRESS OF TABLE IS IN TABADR. FIELD OF TABLE IS
		/ IN TABADR+l.

		CLA
		TAD TABADR
		TAD (66
		DCA TABADR

		TAD TABADR
		DCA INST2
		TAD TABADR+l
		TAD (5000+00+00
		DCA INST1
		PR3
	INST1,	0
	INST2,	0
		CLKADR
		-2
		-1

		TAD CLKADR
		DCA INST4
		TAD CLKADR+1
		DCA INST3
		PR3
		5000+00+00
	INST3,	0
	INST4,	0
		CLKCAL
		-4
		-1

		/ ALL DONE. NOW THE CLOCK CALENDAR IS IN CLKCAL.