;Sept 2016 Herb Johnson ;Chuck Yakym's alternative Tiny BASIC cold-start, ;to speed up discovery of RAM ;provided with permission 0000 ORG 0 INCL "1802reg.asm" ;R0-RF defined HRJ ;HRJ A18 wants register names defined... 0000 R0 EQU 0 0001 R1 EQU 1 0002 R2 EQU 2 0003 R3 EQU 3 0004 R4 EQU 4 0005 R5 EQU 5 0006 R6 EQU 6 0007 R7 EQU 7 0008 R8 EQU 8 0009 R9 EQU 9 000a R10 EQU 10 000b R11 EQU 11 000c R12 EQU 12 000d R13 EQU 13 000e R14 EQU 14 000f R15 EQU 15 0000 R0 EQU 0 0001 R1 EQU 1 0002 R2 EQU 2 0003 R3 EQU 3 0004 R4 EQU 4 0005 R5 EQU 5 0006 R6 EQU 6 0007 R7 EQU 7 0008 R8 EQU 8 0009 R9 EQU 9 000a RA EQU 10 000b RB EQU 11 000c RC EQU 12 000d RD EQU 13 000e RE EQU 14 000f RF EQU 15 ;from Tiny BASIC 000d PZ EQU 13 ;register, BASIC PAGE 0 POINTER 000a AC EQU 10 ;register, MONITOR MEMORY POINTER 0013 BS EQU +13H ; BACKSPACE CHARACTER 001c CONST EQU 001CH ;addr to addr of monitor 0800 PAGE: EQU 0800H ; WORKSPACE BEGINNING ADDRESS 0022 STACK: EQU +22H ; WORKSPACE, HIGHEST LOW-ORDER ADDRESS OF USER RAM 00b0 ORG 00B0H ;cold location for RCA Tiny BASIC ;-----------------------------------------------; ; COLD & WARM START INITIALIZATION ; ;-----------------------------------------------; ; ; ; DETERMINE SIZE OF USER RAM 00b0 f8 00 COLD LDI HIGH CONST 00b2 ba PHI AC ; GET LOW END ADDR. 00b3 f8 1c LDI LOW CONST ; OF USER PROGRAM 00b5 aa PLO AC ; RAM (AT "CONST") ;RC POINTS TO MEMORY THAT HOLDS THE START OF USER MEMORY 00b6 1a INC AC 00b7 1a INC AC 00b8 1a INC AC ; SET AC TO +3 OFFSET ADDRESS ; NEEDED WHEN THE PARAMETERS ARE TRANSFERRED ;ADDED TO PRESERVE SIZE OF THIS PATCH 00b9 c4 NOP 00ba c4 NOP 00bb c4 NOP 00bc c4 NOP 00bd c4 NOP 00be c4 NOP ; FIND TOP OF MEMORY (NEW) 00bf f8 ff LDI 0FFH ; LOAD D WITH FFH 00c1 b2 PHI R2 ; LOAD R2.1 WITH D 00c2 a2 PLO R2 ; LOAD R2.0 WITH D , R2 = FFFFH 00c3 f8 00 SCAN LDI 00H ; LOAD D WITH 00H 00c5 52 STR R2 ; WRITE BYTE 00 INTO MEMORY POINTED TO BY R2 00c6 02 LDN R2 ; READ BYTE INTO D POINTED TO BY R2 00c7 3a d1 BNZ SCAN1 ; IF NOT ZERO THEN GOTO THE NEXT LOWER PAGE OF MEMORY AND TEST AGAIN ; FOR RAM MEMORY 00c9 f8 ff LDI 0FFH ; LOAD D WITH FFH 00cb 52 STR R2 ; WRITE BYTE FF INTO MEMORY POINTED TO BY R2 00cc 02 LDN R2 ; READ BYTE INTO D POINTED TO BY R2 00cd fd ff SDI 0FFH ; SUBTRACT FFH FROM D 00cf 32 d7 BZ SCAN2 ; IF ZERO THEN TOP OF RAM MEMORY FOUND 00d1 92 SCAN1 GHI R2 ; PUT R2.1 INTO D 00d2 fc ff ADI 0FFH ; SUBTRACT FFH FROM D 00d4 b2 PHI R2 ; SAVE BACK TO R2.1, R2 NOW POINTS TO THE NEXT LOWER MEMORY PAGE OF RAM 00d5 30 c3 BR SCAN ; RAM MEMORY NOT FOUND YET ; TOP OF MEMORY SAVED IN R2 00d7 ed SCAN2 SEX PZ ;R2 = TOP OF MEMORY 00d8 f8 08 LDI HIGH PAGE ; RAM SIZED: SET 00da bd PHI PZ ; POINTER PZ TO WORK AREA AT 256 BYTES UNDER THE USER DEFINED ADDRESS 00db f8 23 LDI STACK+1 ; 00dd ad PLO PZ 00de 82 GLO R2 ; STORE RAM END ADDRESS 00df 73 STXD 00e0 92 GHI R2 00e1 73 STXD ; GET & STORE RAM BEGINNIG 00e2 2a DEC AC ; REPEAT TO COPY PARAMETERS.. 00e3 2a DEC AC ; - POINT TO NEXT 00e4 0a LDN AC ; - GET PARAMETER 00e5 73 STXD ; - STORE IN WORK AREA 00e6 8d GLO PZ 00e7 fb 12 XRI BS-1 ; - TEST FOR LAST PARAMETER 00e9 3a e3 BNZ $-6 ; - ..UNTIL LAST COPIED 00eb f6 SHR ; SET DF=0 FOR "CLEAR" 00ec c8 LSKP ; ; "WARM" Tiny BASIC code will follow below. ; 00ed END 000a AC 0013 BS 00b0 COLD 001c CONST 0800 PAGE 000d PZ 0000 R0 0001 R1 000a R10 000b R11 000c R12 000d R13 000e R14 000f R15 0002 R2 0003 R3 0004 R4 0005 R5 0006 R6 0007 R7 0008 R8 0009 R9 000a RA 000b RB 000c RC 000d RD 000e RE 000f RF 00c3 SCAN 00d1 SCAN1 00d7 SCAN2 0022 STACK