Switching memory.

A huge friendly greeting to you, Andrey!!! One day, rattling the keys, numbers somewhere 08/27/97 exactly at 20:47 Andrey Senichkin wrote to All: AS> Greetings, dear ALL !! AS> Since we don’t have echo for dummies AS> have to write here. So where else, if on the topic of echo??? AS> Maybe someone can help me: describe the ports AS> to switch memory on Scorp and write- AS> there is a program for this. ============ bite line =================== So, yes. Scorpion's upper memory distributed next way: eight pages 16 kB in size (16384 bytes), connect- transferred to the 3rd bank of the processor (address simple space 0c000h..0ffffh) via standard port ZX Spectrum-128 07ffdh. Purpose bit of this port: D0..D2 - RAM page number; D3 - switching the address of the start of the screen areas: 0 - 04000h, 1 - 0c000h; D4 - ROM switching: 0 - ZX128, 1 - ZX48; D5 - 0 - does not change anything, 1 - blocks further port configuration. Now more details. Page numbers change - from 0 to 7, with page 2 always displayed in the 2nd CPU bank (08000h..0bfffh), and page 5 is in the 1st CPU bank (04000h..07fffh). In total, we have at our disposal the following pages: 0, 1, 3, 4, 6, 7.In page 7, the first 6912 bytes may position the picture, turn on the display which can be changed by setting bit D3 of port 07ffdh. Bit D4 is cleared when the extended BASIC-128 interpreter, so when the work of user programs this bit must be installed (sometimes, however, sometimes it is necessary to use some other advanced interpretation routines tator, then this bit is reset). Bit D5 is set if it is expected block output to port 07ffdh for pre- preventing its reconfiguration. This is necessary for example, for programs that use a buffer printer (usually a BASIC-128 interpreter uses the printer buffer as an additional area for the interrupt routine). Connect any memory page very simple: LD BC,#7FFD ;enter the port address in BC LD A,%00010000 ;connect ; page number ; 0 and turn it on ; ROM ZX-48 OUT (C),A ;actually output to the port Before outputting to port 07ffdh, you must disable interrupts with the DI command, and then do not forget to resolve them - EI (if, of course, Yes, they were allowed before). In hexadecimal number system the above action is even more clearly implementable: LD BC,#7FFD LD A,#10 ;0th page OUT(C),Awhile the remaining pages are connected outputting the following numbers: #11 - 1st #13 - 3rd #14 - 4th #16 - 6th #17 - 7th And in order to “rigidly” switch to the 48th mode, you need to write the number %00110000 to the port or 48 in decimal - it’s immediately clear what is needed 48th mode... Now - "Scorpio" pages. They all connected to the same address simple- 0c000h..0ffffh, there are also eight of them, but now they can all be used. Pe- Switching Scorpion's pages makes a port 01ffdh: D0 - ROM blocking in the area of the 0th bank of the CPU; D1 - select Expansion ROM; D2 - used for output via RS-232C; D4 - RAM expansion: 0 - pages 0..7, 1 - pages 8..15; D5 - CENTRONICS strobe. Bit D0 controls the connection of the ROM to the ad- in the natural space of the 0th CPU bank (00000h..03fffh). Installation - and instead of ROM one of the RAM pages is installed (using provided by the iS-DOS Chic system). D1 also controls the ROM, connecting in place previously located "Scorpio" ROM. Used, for example, to determine versions of the Shadow Service Monitor. D4. Now we have reached this level. It connects in place of the 3rd CPU bank page with number "pg+8", where pg - country nitsa established earlier by output to the port 07ffdh. In other words, to establish for example, the tenth bank of RAM, you need to execute next program: LD BC,#7FFD LD A,#12 ;10 - 8 = 2OUT(C),A LD B,#1F ;BC = #1FFD LD A,#10 OUT(C),A and to remove the standard configuration, you need to do: LD BC,#7FFD LD A,#10 OUT(C),A LD B,#1F XOR A ;A = 0 OUT(C),A And don't forget about interruptions! ============ bite line =================== AS> Thanks in advance!!! You're welcome... ;-) Best regards, Yuri. -+- iS-DOS v4.5 with macro

Hello Andrey!!! One hot summer evening, like 08/27/97, exactly at 20:47 Andrey Se- nichkin wrote to All on the topic 'Perek- Losing memory.': AS> Maybe someone can help me: describe the ports AS> to switch memory on Scorp and write- AS> there is a program for this. Yes, in general, there’s nothing to switch here, just take and set the D4 bit to port #1FFD, and you get a page- the one with the number 8 is larger than it was. Hap- For example, there was 0 page, now - 8; was - 2, became 10. For example, you need to set page 10: PAGE LD A,#12 ; turns on 2 pages. LD BC,#7FFD OUT(C),A LD B,#1F ; turns on 10 pages. LD A,#10 OUT(C),A RET That's all ;) AS> Thanks in advance!!! Yes please ;) With best wishes, Dmitry. -+- Board 4.5 meters long