{File name:  Protected.mc

Last Edited: Amy Fasnacht November 16, 1981  2:22 PM: Change register names
Last Edited: Jozef Furst November 4, 1981  3:18 PM: multiple allocation corrected (Carry changed to RefCarry)
Last Edited: Amy Fasnacht October 23, 1981  11:40 AM: Change register names to prevent conflict with SAx00Initial.mc names
Last Edited: Amy Fasnacht September 11, 1981  9:52 AM: make clock update atomic
Last Edited: Jim Frandeen August 19, 1981  4:30 PM: add clock update to refresh task.
Description: Protected microcode for Initial,
Author: Jarvis,
Created: December 5, 1980,
}
jk20(0,4939)(1,5644)(2,6350)(3,7056)(4,14817)\f1
Set[OverlayStart, Add[ProtectFence, 1]];

Reserve[OverlayStart, 0FFF];
	{
	Phase0Protected (Protected.mc, IOPBoot.mc) resides in 0 - 00FF
	Phase0 (Phase0.mc, DiskBootDLion.mc, EtherBootDLion.mc) resides in 0100 - 0FDF
	The BootKernel resides in 0FE0 - 0FFF
	Part of the BootKernel that can be overlaid resides in 0FD8 - 0FDF
	}

SetTask[0];

{clobber only rC before going to external fault handler}

Trap:	rC_ RRot1 ErrnIBnStkp, ClrIntErr, CANCELBR[$, 0F],	c1, at[0];
	[]_ passTraps, ZeroBr,	c2;
	BRANCH[$, Trap1],	c3;
	GOTOABS[ErrorHandlerLoc],	c1; {pass the trap on}
Trap1:	acR_ bootTrap, GOTO[catchAll2],	c1;

catchAll1:	Noop,	c1, at[Maintenance1Loc];
catchAll2:	Noop,	c2, at[Maintenance2Loc];
catchAll3:	rB_ 0, rBrh_ 0,	c3, at[Maintenance3Loc];
	MAR_ [rBrh, rB+1],	c1;
	MDR_ acR and 0FF, CANCELBR[$, 0],	c2;
	IOPCtl_ IOPInMode,	c3; {enable IOP}
infinite:	GOTO[infinite],	c*, at[IdleLoc];

SetTask[1];  StartAddress[Refresh];

	{We come here once per line, or every 28.8 usec. 
	That means 34,722 times per second}
Refresh:	rJ _ rJ - 1 {Decrement clock low}, ZeroBr, Refresh, CANCELBR[$, 0F],	c1;
	BRANCH[NoCarry, RefCarry],	c2;

RefCarry:	rG _ rG - 1 {Decrement clock high}, GOTO[TestTimeout],	c3;
NoCarry:
	Noop,	c3;
TestTimeout:
	Ybus _ rJ or rG, ZeroBr, Refresh,	c1;
	rN _ 1, BRANCH[$, Timeout],	c2;
	ClrDPRq, GOTO[Refresh],	c3;

Timeout:	uTimeout _ rN, ClrDPRq, GOTO[Refresh],	c3;


z20320k40(2,14817)(3,65535)(4,65535)\f1 519t2 1t0