MXO-KP50.ASM (MAC)  Revision history:

  2/28/86  5.0  Major rewrite of this overlay, hence the version
		 changed.  Converted all code to lower case, tabified,
		 and moved misc. equ's below this comment section.
		 Heavily edited rev. history to save space in this file.
		 Changed code to use Z80 opcodes to save code space.
		 Separated SIO register storage so, it is now possible
		 to use both modems at the same time, and switch back
		 and forth at will.  Removed all smartmodem support.
		 Fixed faulty NITMOD logic that was only checking to
		 see if the default modem was active, and only
		 initializing that one.  (If you used SET to switch
		 modems, dropped to CP/M, and returned, it could
		 hang up phone).  Cleaned up SET cmd nomenclature,
		 that had gotten confused in the comments and tables.
		 Removed use of interrupts from dialer routine:
		 was crashing 2.2u1 machines, and would lock up a
		 machine without an internal modem if user issued
		 a CALL or DIAL command. Now dialer just inserts an
		 appropriate delay, and assumes chip is done.  (Timing
		 is better: now as fast as the Smartmodem's). Added
		 support for tone dial '#' and '*' chars in dialer,
		 now important for 'cancel call waiting'.  Also added
		 support for flash (exclamation mark), ';' and 'R' dial
		 modifiers.  All behave as on Smartmodem.  Fixed
		 PBAUD so MEX dialer cannot reset baud rate on external
		 when dialing internal (possible before).  Added
		 routine to notify user of a carrier drop, and disconnect.
		 Reason: carrier drop is not always obvious when it
		 occurs on internal.  Added flag to indicate that SET
		 values displayed may not be correct when returning from
		 CP/M (no way to read current params from SIO or CTC).
		 Added code in NITMOD: and SYSVR: to tell user which
		 (if any) modem(s) currently active when returning
		 from CP/M: if one is active (carrier detected), then
		 it is selected, regardless of the default modem.
		 Added stripping of several garbage chars like DEL as
		 they come in from modem, to clean up 1200 & 2400 baud.
		 Added PARITV: and NOPARV: support, to shut off effect
		 of this stripping.  Made SET ?, and other
		 displays and messages more consistent with other MEX
		 messages.  "SET xxxx <blank>" now displays current
		 status of xxxx instead of an error message.
		 MexPlus equate added, but not tested.
		 Added rudimentary internal modem detection, based
		 on DCD floating high after disconnect.
						-- Tim Farley

 ??/??/??  4.3  This version, though mentioned in the overlay list
		 and elsewhere, never showed up in my area.  There
		 apparently have been some other later versions as
		 well, but I've been unable to find them, so I went
		 ahead with my release. 	-- Tim Farley

  1/11/85  4.2  Fixed SBREAK and DISCON routines to work properly
		 when parity is set to other than NONE.
						-- John C. Smith

  9/19/84  4.1  Fixed DISCON routine now lowers DTR & RTS for one sec.
		 Added manual busy abort (hit any key) in smartmodem
		 dial routine.			-- Kim Levitt

  NOTE: around this time, the overlay was separated into MXO-K484.ASM
	 and MXO-KPSx.ASM, for separate internal and Smartmodem
	 overlays.  This was done to make the overlays more
	 adaptable, but compression and editing of the existing
	 code had not been throughly pursued.	-- Tim Farley

  9/9/84   4.0  Added internal modem SET PARITY, STOPBITS, and LENGTH.
		 Fixed internal modem auto-answer logic so it works.
		 Corrected error when setting STOPBITS to 1.5, which
		 was resetting parity.	Now fully duplicates SUPRTERM
		 support.  Enhanced SET MANUAL for internal modem.
		 Version level changed to eliminate confusion between
		 2.X and 3.X overlays.	Updated comments & documentation.
						-- Terry Carroll

  8/26/84  2.8  Added equate to support Anchor Signalman Mark XII modem.
		 Affects DSC, dial abort and SET DELAY.  Added the
		 PARITY, STOPBITS and LENGTH commands from the Norm Saunders
		 overlay (MXO-KP3x), for external only.  Added modem id
		 to SET ? command.		-- Terry Carroll

  8/03/84  2.7  Added call to DISCON: (disconnect routine) in the
		 Smartmodem dialing routine.  Avoids connect that comes
		 right at timeout.		-- John C. Smith

  6/10/84  2.6  Undid revision 2.5.  Both DCD detect on entry and
		 internal modem initialization had been commented out.
		 Cleaned up code in NITMOD: for PIO init and RS-232 init.
						-- John C. Smith

  6/03/84  2.5  Commented DCD status check	Dennis Quinn
		 at NITMOD2, so Hayes could	Royal Oak, MI
		 be used at factory settings.

  6/02/84  2.4  Code was turning off RTS	Dennis Quinn
		 after disconnect sequence.	Royal Oak, MI
		 This was causing problems
		 with certain modems.  Enabled 110 baud operation.

  5/31/84  2.3  Changed code to be compatible	John Smith - Manlius, NY
		 with the older Kaypro models
		 enabled 19,200 baud operation.

  5/29/84  2.2  Corrected SET ? to display	Steve Sanders
		 proper SET ORIG command instead
		 of SET ORIGINATE

  5/28/84  2.1  Added conditional for old	Steve Sanders
		 Kaypro 2/4

  5/27/84  2.0  Added internal modem and	John Smith - Manlius, NY
		 revised SET commands.

  5/18/84  1.0  Original version		John Smith - Manlius, NY