80-Bus News

  

November–December 1983, Volume 2, Issue 6











Page 16 of 67











16

Some of the above I got from Belectra’s part of the documentation, which is clear, if rather brief; much of the rest of the information about the 9511 came from “Modern Microprocessor System Design” by Daniel R McGlynn. Also included in the information Belectra give you are details of the ports used by the board, but there is no need to repeat them here. If you do reconfigure the board to other ports, you can easily patch the Pascal compiler’s run time routines to take account of this, as the address of the data port is stored at £0103, and the address of the control port is at £0104. (Quoted from Hisoft’s “Functional Differences between Hisoft Pascal 5D and Hisoft Pascal 4D”, which comes with the Pascal manual.)

Belectra’s documentation gives brief but very clear examples of how to program the board using Z80 assembly language, and it is clear that this is quite an easy job, when compared with writing your own set of floating point routines. The thing is, the rest of the program is going to be a bit of a pig, if it uses the calculations the board can do, to any great extent. I once wrote a biorhythm program in 1K of Z80 code (and I hasten to point out that I do not believe in biorhythms!), and it was no fun at all, especially the bit- that drew the sine waves. So I will move hurriedly on to the sensible way of doing things, namely with high level languages, pausing only to note that if you do program the board in assembler, then there is no reason why the Z80 can not get on with something else while the HSA-88B is working. For instance, it could be preparing the next data to be worked on. It could just as easily be controlling another HSA-88B, if you have the money to run more than one of them! Then you would need to write some nice queue handling routines, especially if there was another board that also ran independantly, like the Pluto. I think you had better forget that sort of programming style, unless you are a real masochist. After all, you are supplied with Hisoft Pascal 5 along with the board, and Hisoft’s compilers are renowned for the speed of the code they produce. HP5 uses the HSA-88B for all its arithmetical work, which means that as well as compiling programs that run faster, it also needs a lot less memory space for its completely rewritten run-time routines. (Sometimes you can have your cake and eat it too!) If you want to use some other compiler with the board, or even an interpreter, this is possible, as long as you know how to do things like modifying the run-time routines the compiler churns out, or finding the bit of the interpreter you need to change. Belectra give brief notes about what is required, but also say “The only remaining consideration is whether a particular compiler or interpreter is worth modifying; some generate code which is so inefficient that even if the HSA-88B performed its function in zero time there would not be any noticeable difference in overall program execution speed.” I haven’t tried the patch to MBASIC from the last issue, as I can’t afford MBASIC...

Hisoft Pascal 5D is supplied with the manual for the earlier 4D version, and six pages of notes concerning the differences between the two compilers, marked “provisional” on my copy. The major change, obviously, is the use of the HSA-88B for all arithmetic. This includes integers, all of which are now to 32 bit precision. As a result of this, MAXINT is now 2,147,483,647, which is a big number! I am not at all bothered by the compiler’s inability to handle recursive WITH statements, though there is bound to be someone, somewhere who thinks this is a fatal flaw! Instead of RANDOM, you now put RANDOM(X), where X is either zero, or a seed for the random number routine. If you use 0, the value returned is between 0 and 65535 inclusive, rather than the old 0 to 255. GOTO (whatever that is) can not transfer execution to another block. I haven’t written a GOTO in Pascal yet, and if I ever need to, I will be quite surprised. The provisional manual gives the addresses in the


This is an OCR’d version of the scanned page and likely contains recognition errors.











Page 16 of 67