68 lines
2.8 KiB
Text
68 lines
2.8 KiB
Text
THE Z80 BACK END TABLE
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INTRODUCTION
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This table was written to make it run, not to make it clever!
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The effect is, that the table written for the intel 8080,
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which was made very clever runs faster and requiers less space!!
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So, for anyone to run programs on a z80 machine:
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You could try to make the table as clever as the one for the i80,
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or you could run the i80 table, for that can run on every z80 too.
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IMPLEMENTATION
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It will not be possible to run the entire Amsterdam Compiler Kit on a
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Z80-based computer system.
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One has to write a program on another
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system, a system where the compiler kit runs on.
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This program may be a mixture of high-level languages, such as
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C or Pascal, EM and z80 assembly code.
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The program should be compiled using the compiler kit,
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producing z80 machine code.
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This code should come available to the z80 machine
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for example by downloading or
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by storing it in ROM (Read Only Memory).
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Depending on the characteristics of the particular z80 based system, some
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adaptions have to be made:
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1) In 'head_em': the base address, which is the address where the first
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z80 instruction will be stored, and the initial value of the
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stackpointer are set to 0x1000 and 0x7ffe respectivally.
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The latter because it could run on a 32K machine as well.
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Other systems require other values.
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2) In 'head_em': before calling "_m_a_i_n", the environment
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pointer, argument vector and argument count will have to be pushed
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onto the stack.
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Since this back-end is tested on a system without any knowledge
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of these things, dummies are pushed now.
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3) In 'tail_em': proper routines "putchar" and "getchar" should
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be provided.
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They should write resp. read a character on/from the monitor.
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Maybe some conversions will have to be made.
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The ones for the Nascom and Hermac z80 micro's are to be found
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in the EM-library.
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4) In 'head_em': an application program returns control to the monitor by
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jumping to address 0x20.
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If this is not the right way on your system, change it.
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For an CPM-machine for example this should be 0x5, to provide a warm boot.
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5) In 'tail_em': the current version of the z80 back-end has very limited I/O
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capabilities, because it was tested on a system that
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had no knowlegde of files.
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So the implementation of the EM-instruction 'mon' is very simple;
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it can only do the following things:
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Monitor call 1:
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Exit
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Monitor call 3:
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read, always reads from the monitor.
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echos the read character.
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ignores file descriptor.
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Monitor call 4:
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write, always writes on the monitor.
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ignores file descriptor.
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Monitor call 5:
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open file, returns file descriptor -1.
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Monitor call 6:
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close file, returns error code = 0.
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Monitor call 54:
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io-control, returns error code = 0.
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If the system should do file-handling the routine ".mon"
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should be extended thoroughly.
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