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/ TIMELINE? IS HOG SIX! PATOF / AAPPY BIRTHDAY TINELINEZ, / This months coluan vill be brief. We received in the pail what ve felt is important information con- cerning the expandability of the TINEXsinclair 2868. If any questions result from your reading, please consult your inquiries to:

fir. Willios J. Pedersen 1128 Merrifield 5.E. Grand Rapids, MI 49567 The VIOQUUP Co. Please excuse the size of text used. This arti- cle is extreeply large.

On another note: Storting in Rugust, the TINEX- sinclair Cambridge Silicon Valley Users (pheu!

a lot of vords) will have their aeeting on the third Wednesday of each month. filsa, there ore tuo more BES's vithin our area. Let's show our support and give them a call!

The TIMEXsinclatr 2068 By Billian J. Petersen

fear Survivor,

The enclosed article regarding expanded bank suiiching is of such importance that I om sending it fo several neus letters to avoid delay vith exchanges.

It is high time thot pemory and back-plone expansions become available and knoun.

The VIDUUP Co. is thereby making the original design public in the hope that it will get the ball rollins.

In the interest of economy and availability, tuo (tems should be accepted as an interia standard.

€9:6.66.0666.6.00666666666006 x RENINDER . The July/August TINELINEZ is Ya bi-monthly issue to maintain ¥ Ya 10-year subscription balance \

KIKI KIKI III KIKI KKK

BILINIEZ

ISSUE 65,86

MAY/ JUNE 1989 $1.56

a TIMEX/sinclair User Croup Nevs—Mageazine x

The TIMEZsiaclair 2868 Coat.

1, Bock-Plone EVEREX SYSTENS INC. EV-168) 2. fidapter VIGRP Co. Gesign

This bock-plane is a standard PC expansion board having eight slots; one of vhich aust be used for the BSC. There is no need to sake things difficult.

The adapter plugs into the rear connector and has the usual feed-thru. It has a cable take-off for connection to the BSC card, and some other convenience features. Design information will be available from the WIDUP Co. It is hoped that someone vill produce it. Prototypes have been aade and examined at conventions for a couple of years, so this ites should be nothing nev.

There is one gore thing that should be stondordized, though the reasoning for it is not immediately evident. The pin assignsents for the back-plane, being arbitrary anyway, vill correspond closely vith the IBN bus. The reason?

The BSC can easily be modified for use with some PC clone cards. Vhy rot hove upuard compatibility right from the stort. This is NOT a plug for IBM or the PC clones! It is a simple econcey weasure uhich is in the interest of all TS2068 supporters. There is no easier uay to get ports, timers, and godess than this.

It will be o long tise before users util be ready for a full-fledged auto-configuring system vith a DAISY CHAIN, ond the advanced BSC that requires, if ever. Hopefully a clove vill come along having this built in. If anyone is doing thot, I bea him to contact se. It EXISTS, regardless of uhat people have been saying. (It requires the EVEREX expansion boord for the AT or eqivalent.)

Don't let this revolutionary development get quay! PEMORY IPROVES ITE ACE ?

Crazy? Perhaps so, but survival of our favorite antique 152869 computer depends on it to a degree. Tuo advances ore prisarily responsible for this. Both extend the amount ond speed of avail- able sesory, over and beyond that in the DOCK bank.

fisc drives igprove speed, accessibility and convenience over tape recording.

RAMDISK has broken all speed records and has expansion possi- bilities uhich ore impressive.

Nou all ve need to do is find some vay to bank suitch addition- al memory. It has been said it can't be done because TIMEX expertise has been dispersed —- DINOSAUR CHIPS !

Uhile it is true that the system TIMEX intended (before killing iD is highly complex, it is NOT the only system uhich vorks. The one described in Figures 1 ond 2 is just about the siniaum bank suitching system. There are a lot of features like handling interrupts and autoconf iguring thot are beyond it, but it can address 16 megabytes of memory ard vorks vith the unmodified TS2068, camila

‘ 3 TIMELINE? news-magazine is publ ished TIMNEXsinclair || and is © Copyright 1989 by American Micro Systems, Sam Jose, CA 95121. user group TIMELINE? may be freely copied for non-— Neu Mm : a use Sp bb iieeesr gt tol in a whole or in par or commercial means > agactne is prohibited by lav. GIVE CREDIT!!!

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THIS PROCRBN. || NOTICE: Contributors to TIMELINE? ore independent of American Nicro Systems ee ond opinions expressed in the contents of this publication are not necessarily those of the manageaent staff or its advertisers. American Micro Systems DESK-TOP PUBLISHING vill not be held liable for any dosage or consequences resulting from instru- FOR THE SINCLAIR OL ctions, assertions of foce, revieu of products or companies provided in the ss SS se se BOOZ ine 's content. It is recommended that anyone atteapting to podify their RP tiene ae computer or constructing an electrical project should seek ee from more

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IMELINE?

The TiMEXZsiacleir 2862 Cent, PEM@RY BARK Figure 2)

There is nothing porticularty special about this sesory bork. Tt decodes a 24 bit address and hos a dip-suitch to locate 64K of contiguous memory space at any 64K boundary.

If any of it’s memory is active, it drives the BE signal tow to disable LOCAL HOME, EXROM and GOCK banks. Vith this system it is impossible for tuo expansion banks to be on the bus at the some instant. Gee Appendix A for greater detail.)

SYSTEM CONF ICPRATIGN

There ust be some voy to MAP all or port of memory.

The simplest way to do this is to urite programs uhich assume continuous semory up to a variable Limit, and uarn uou uhen that timit is exceeded. For this, each expansion bank should have dip suitches set from 1 to HARBAKK in sequence.

There are better wrys vhich allow unused available banks to be suliched around uhere needed: saving $494. This needs some progromaing overhead, but you hove ROOM for it.

WUTG-COM ICRRRT IGN

This is where the computer is programmed to 90 out tc explore the neighborhood, Yhatever it finds is recorded into a systes configuration table (SYSCON for later reference.

THIS 1S NOT EASY!

A DUNE device cannot be found because it cannot onsuer a roll- cali. It is deaf to attention-setting methods. It con be sade visable by attoching a baby-sitter chip which con respond and identify itself and the attached device.

A SMART device listens, answers, and often calls for attention Stilt, it aust also accept an order to shut up so it von't interrupt. The IEEE488 system is a system for standardizing Command larguage betueen uidely different computers and devices, but it is still not smart enough to keep quiet vhen another: device uith the some ‘name’ is on the system bus.

Duplicate noses can be resolved if they are at different addressatile locations. In this uy, one of the names con be chanced to avoid future confusion and vasted time. It only needs to be done initially, or vhen some outside event has created another duplication Like turning on a disc drive),

A DAISY CHAIN is one way to rescive the unique address probles

Another common method is to give back-plane slots an address on a temporary basis. (Perhaps expandable using a DAISY CHAIN.)

Both methods assume sogething about the desion of the connect- i NETWORK. It gust guarantee reaching onlu one device at a

ime,

BE TUGRK INC

Almost by definition, a netuork is uhere Murphy lives. Frequently the unexpected happens. Ho aore than three points vill be made here,

1. Statistical methods sust be used to find time slots uhen

but confusion is absent by chance.

2. If this uorks; there is no need for physically unique

addresses, though default nomes still heip.

3. Airey device cormected to a netuork can help by introducing

a rondos delay that is natural to the sustes.

BANK SBITCHING

A bank suitching controller @SC) is essentially a netuork suitchboard. The 752868 operating systes expects eight equal & wide channels assigned arbitrarily to CHUNKS.

The 788, like sost CPs, has channels to internal registers: ond internally suaps betueen register sets. It is a bank ' guitching controller tiself.

461

Machine code includes extended addressing provided by addition- al fetched butes. Prefix bytes allow instruction sets to be bank suitched.

The 8868 CPU used in the IBM PC and clones has four dedicated internal bank suitching registers uhereas the 2788 has none. This idealistic approach for the 8888 uorked Like a chore until it ron into deep vater. It outgreu it’s island and couldn't build @ boat Externally, bank switching registers do not hove these lisite- tions.

The BSC in Figure 1 is similar to the one inside the 8888, but there the resemblance ends. It has eight channels instead of four, and can address sixteen times os such space.

There are better B5Cs than the one in Figure 1, but this one does a POMERFUL job. It also requires no alteration of your precious 152068, a good compromise,

BANK SUITCHED OPERATION

The gost significant three bits of Z88 address space are used to select one of eight previously established address extension bytes in a current chunk ouner toble (CC0T). The reacining bits address locations vithin each & channel.

hen power is first turned on, ond at cther times vhen the 752068 needs exclusive control, COOT aust be turned GFF. Turning it GR could be a probles.

Fortunately ve can first assign all eight channels to HOME. The extended address is 255 for uhich nothing usually responds. Then nothing happens vhen CCOT is turned GN. The ‘usually’ reference is explained later.)

Vith CCOT turned OFF extended address bits ficat, unless some- thing is conmmected to force them high. In effect, the GFF condi- tion also gives 205 for the extended address. That is exactty uhy HONE bank vas assianed that bank rember.

ROM SUTICHING CORTRGL

Except during pover-up there is no safe place in physical gemory to put bork suitching code. Oniy the fetched instruction in the 288 is immune. That instruction aust be able to find the BSC recardiess of memory assignments. It aust use 1/0 (another example of 288 bank switching). Because 0 TO and CALL are not 170 instructions, and the sachine stack is unsafe anyway, each bark chunk using these needs ta support thes vith MACROS having the same effect. The some applies to the RETurn instruction.

The sost elegant method avoids using these by continuing the code in the shadoving bank and leaving the chunk vith the current gochine stack untouched.

This flexibility is uot makes multitasking and sultiuser tine shoring systems remarkably easy to create. Each user con have his cun private partition under contro! of a SUPERVISOR. Security from program interference resains a problem vith the 208, not like other CPs uhich provide privileged instructions. Certain programming conventions will have to be folloud to compensate for this.

There is great pressure to reserve one chunk to one bank to hold the system variables (SYSUARs), machine stack and bank suitching routines. This is the technique used in the relics of mochine code remaining in the unmodified 152068. If repeated in each user's partition, this is a 900d convention te use. It should be remembered thot it is still a convention, and need not be followed.

The relics use semory mopped bank suitching ports. Untess these port addresses are forbidden to be used in all bonks, it doesn't vork. The BUG consists of stacking the port byte from one bork and restoring if in another, thereby destroying it in the neu bork. There is a uy to suitch stacks to resolve this probles, but is too complex for serious considerations.

IMELINE?

The TifkXsiaclair Coat,

Global SYSUARs can be stored in 1/0 space; so this is not a real difficulty. The same applies to o bonk switching stack run by the MACROS atready sentioned. An alternative for the bank switching stack is to dedicate a fixed bank and chunk for it, though this has the probles of not remaining safe from accident.

POST GF THIS BOES HOT APPLY 16 THE SC IN Figure 1. IT MS BEEN IMCLOSED 76 SROU BRAT CRN RE BONE WITH A MORE SROANCED PERS IGN. eee

Control is simple. This BSC is urite-only. It has eight ports of vhich only four are presently used. The port assignments avoid those to which the ZX and 15204@ printers respond and all known physical interface ports like the HODEN ond TASMAN.

PORT OATH FUNCTION

132 x Turn COOT CFF

133 x Turn COT H

134 Blank # {uner to be posted ta CCOT ix "HS" CHUNK mask, active LQ

Bars # is identical to the extended address byte. (UT 134, Bonk # urites the bank number inte a register uhich maintains if as input to CCOT. “Ho” ts the “Horizontal Select” described by TIMEX. Looking at the structure of CCOT, it aake sanse, QUT 135, HS latches the stored Bonk # into COUT resisters for which HS bits ore active LO.

some of the more signigicont bits con be ignored in saaller systems, vbich explains vhy EXROM is Bonk # 254 ond DOTK is Bonk #6. A system using only the lover nibble can still address one segatyle of memory.

Control can be sofer from accident by using one of the unused ports to act as “SINGH SAYS". This uas the real purpose of the TIMEX RESET NIBBLE SEQUENCE bank suitching instruction, thoush never explained,

EXCEPTIONAL CORBITIONS

Bank numbers from 1 through 2753 ore oravy, but vbot about HOME (755), EXROM (54), and DOCK (8)? Con they be implemented as real external banks? The onswer is definitely yes, vith some limitations.

BO"E ROM con be replaced vith EPROM at the drop of a hat. An almost trivial case is replacing it uith SPECTRUM ROM. What is NOT trivial is the resulting SPECTRUM having bark switching capabilities! Repairs to the 792065 ROM code con be made in EPROM vith impunity. Untike other barks, bank 255 is active ia- medictely at power-up. Because SPECTRUM is a subset of 752868, it remains a toy vith vhich to play. The real pouer lies in in- stalling upuard compatible extensions to BASIC and to restore TIMEX disabled functions like OPEN, CLOSE, RESET, ond CATalogue.

EXROf cannot be directly replaced uithout removing it from the case, ond even then, it is not quailable during pouer-up, The problem vith internal EXRUH is thet it is incompletely addressed so an image of it appears in all chunks, not just chunk @. The addressing probles con be solved by goving the chip to a special cord which plugs into the cartridge stot. This card doesn't Change anything except to provide full addressing to suppress the fase images. Of course, if EXPON is replaced uith EPROM you Can wake repairs to code. In any cases you now have chunks j through 7 of Bonk # 254 (enabled by EXROM sional) ubich you are _ free to use. On the expansion bus bonk # 284 vill have priority over this, but it is not active during initialization.

The TINEIsiacteir Ceat.

BOCK is usually enabled by the ROSCS signal available at the cartridge slot. If you relocate it to the expansion bus os Bonk #@, it has priority uhen OH, or can act the some becouse the POSCS signal is available on the expansion bus.

If you have no back-pione, the EXROM relocation card is the perfect place to include replacement HOME ROM using o technique described in another article for recovering the ROACS signal logically--as it is not available at the cartridge slot.

For the same reason, this card should carry o replacement cord edge connector so you con still use your cartridges.

Should you desire, once the system has been initialized, and you [0 have an expansion bus, even these replacements can be re- placed by the external higher priority back-plane cards. hen this is done, EXROM and DOCK are no loncer mutually exclusive,

SUrPRRY

While the Bark Suitching System described in Figures 1 and 2 hos limits on vhat it can do, it should start a revolution. It is staple enough te understand, uses exsily obtainable parts, and any reasonable competent hardware hacker can build it. It doesn't put your T5206 at risk, and even if EXROM is relocated, there ore no viring changes internally so you can always put it

fi tot of sental suent uent into creating this version. The sain reason for it is ta give the user confidence that it con indeed be done as advertised. Perhaps later someone utlt actually believe that a full self-configuring sustem actually exists fuhich it does).

It nevertheless is one GION] STEP for the TSZ86S.

ONCE TAKEN —— DATCH 08! OPPEMBIS fi

Yhen the clock is speeded up to the point uten memory boards cannot keep up, a “hold it!” signal can tell the system to give it more time until it catches up. This is called HOLU or AIT, depending on the processer GAIT for the 28H).

In a system vhere other bus masters like DMA controllers are present, and there is a good chance some of them will be too fast for the memory, the memory board sust issue VAIT until it has responded properly,

Most of the time a bus aaster vill not be kept uniting because the VAIT pulse has vanished by the time it is checked.

Referring to Figure 2, the active lov BE signal con be used to trigger a one-shot flip-flop to generdte a short delay pulse. Clock cycle delays cannot be used because there is no uy to teil in advance how fast the clock will be running (uhich vas the problem to begin vith). The only advantage of clock cucle detous is vhen a knoun clock speed is too fast, and slo-poke memory chips are used to sove goney. Even in that case, the one-shot method is sore efficient. Exceptions exist uhere mesory boards contain their oun clocks. Core and duramic mesory controller refresh boards belong to this category; and are intermediate tn efficiency because of o random suchronization delay as vell.

Vhen polling for the presence of devices with the goal of map- ping system configuration, neither the VAIT nor BE signals are of any use. In order to read bank status there must be on IAD

‘ port on each reporting device uhich is keyed to the bank number.

The BSC drives the extended address from the selected bork number instead of CCOT. The data returned could be anything, but interrupt pending status ond uhether the bank is ever: there are both sondatory information. These bits sust be active low in case nothing is there. During this read, it is the BSC vhich pulls up the data bus. Device status registers use open collector TTL.

IMEL TNE Za | a3

TS2068 138

NOTE: This unit generates extended address lines to No access over 16 megabytes of memory. It is fully compatible with the unmodified TS2068. Configuration must he defined

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IMELIRE? —

Figure 2: Memory Bank

48y GND +#Sy

RACK Bonk #

Selector ed)

PLANE F $i a eas = ‘ = Y

az3——AL{A2 BB m,n OFF

aze Sjaz © pz ee

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2 3 4 85 3 ol Guess srreasaeke eee sessase sees sig HL | too [orl a "ii

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sft 3 To insure correct bank priority, :

als EQ i. meseeccessccesone ecceecucenne al

=} ffi install jumper for each 8K * 8 a memory chip actually present.

7 t 6 ut 5 He Ne 133 -"

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a me Fe | el Eel cA el 3 Fa) 2s ek te hee ‘hae ee ‘ + |- es | ] 8 4 a t re pe 2 : — poets ; tw es mw nt iin Kl 7 oo 4 '0 i RL tl (cl vt

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Memory NOTE: Menory can be any mix of ROM and RAM, Bonk but if ROM is present, at least chunk 6 7 should be ROM. (for a bank nap)

Ale = - all : 2 aid CDMG6264 (8K = 8)

9 : . " A — ae (Static RAM shown) a7 x NT AE Is AS 2 ri DS ag 2 DM «2 Q2 he De o) é pr! 62 re LF. | #5y) —

IMELINE

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Hay 13, 1989 fugust 12, 1969 July 8, 1989 October 14, 1989

INELINE? ~

The TIMEXsinclatr Coat. is 7 Votuse &, Nuaber 5 SinclLink TINDER ha’ :8s

Ain 170 urite to a bunk resets the interrupt pending register. This vill also reset the INTerrupt bus signal if no other devices have interrupts pending. Interrupts issued by devices

not currently ouning chunks are easily found this uy so their | 1989 May @8 17:11:98 Sn89_filesss.. borks con be enabled tc handle the interrupt. A bork number list | flpi_sn895_lts OF ilename_ext Bytes.. is used to service interrupts in priority sequence. fn interrupt | $°892588.17873; Yords 19873; ee not found in a configured bank or for the keyboard means that a SincL inks; Neusietters; 9n89_dir 193386.. new device has come on line and the aute-conf igure procedure Fitename_sn895 (Sn834).. SnB95_lis UMo2.. aust be done again. naan ScBIH4_lis SB... For contact Sy89t88_lis 21448.. Uhen a DAISY CHAIN is used, the Bank # dip switches are replaced | Sincink.. SxB9tGpG_lis 2404.

vith a urite-only ond clear 1/0 port register so each card con be assigned a unique “nome”. This 1/0 port is enabled by the status of the DAISY CHAIN. A global 1/0 write resets both the DAISY CHAIN ond the “nase” registers, Bank # @ cannot be used with a DAISY CHAIN system and special provisions are needed vhen HOME and EXROM are relocated anywhere but the cartridge slot or equivalent,

(ce the current DAISY is named, it con be addressed directly to read status, and written tc if applicable. When o nonexistent Daisy is given a nome and then asked for status, there is no ansuer of course. This signals the end of the CHAIN.

6 1986 Villiom J. Pedersen

THE SOFTWARE CORRECTION c/o Charles Ridguay 2816 Chestnut

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ee ce ls ne a le a A TRA SS A AS TE SD AS A

Sr895 table of contents

(INSIDE) 33...

page. description... 2. SLIX contacts and neusletter

exchanges, April 1989 G3?) (Sc8904) ..

5. SINCLAIR USER GROUP LIST

Paortial- because of lock of space, the following groups are omitted:: Isreals: Mexicos; Nev Zealands: Noruays; Pokistons; Portugalss Singopore:; && Spain) (Ssh95G8a) ..

7, SLIX Indexing Proposal by Tin

Suerson (Gs83417a)..

The follouing articles are rot

included in the paper neuslette for lack of room. They are available on disks;..

% Information Helpful in Writing

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t How ta Use USENET Effectively

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Sné44_dir GBt66?.. Sn44_tis = 15M... Sx89t8pG_ lis 2876.. Sc0003_lis 48i46.. RnG94t3_lis 16498..

S893.dir 987677... S093 lis 13354... ScO98@2_lis 39088

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