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Merge table for zero page into main memory table

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Nero 2019-10-27 18:44:38 +00:00
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README.md
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@ -17,36 +17,27 @@ On a 8080, there are no segments, the addresses are as displayed.
On on the 8086, a single segment with a value of 0x0100 is assumed.
This implies that the first 4k of memory are not used.
The BIOS and FDOS may be recompiled for starting at a lower address, in this case,
The BIOS and BDOS may be recompiled for starting at a lower address, in this case,
the minimum memory requirement may be less than 64k.
|Start|Size|Function|
|--|--|--|
|0xF800|2k|BIOS / hw drivers|
|0xF000|2k|BDOS|
|...|...|BDOS data area, disk deblocking buffers|
|SP|var|Stack, growing down|
|...|...|Free memory|
|...|var|Heap, growing up|
|0x0100|var|Transient Program Area|
|Start |Size |Function|
|------|---------|--------|
|0xF800|2k |BIOS / hw drivers|
|0xF000|2k |BDOS|
|... |... |BDOS data area, disk deblocking buffers|
|SP |var |Stack, growing down|
|... |... |Free memory|
|... |var |Heap, growing up|
|0x0100|var |Transient Program Area|
|0x0080|128 bytes|Command line and disk buffer|
|0x0008|120 bytes|BIOS data area|
|0x0000|8 bytes|BDOS data area|
|0x0005|3 bytes |Jump code for BDOS|
|0x0004|1 bytes |default drive for BDOS|
|0x0003|1 bytes |may be used as iobyte by BIOS|
|0x0000|3 bytes |Jump to BIOS warm boot entry point / program exit|
## Application program interface
It is using the `call 5` convention with CP/M compatible syscall numbers.
File I/O is done via FCB blocks.
## Zero page
|Offset|Size|Usage|
|--|--|--|
|0x00|3 bytes|warm reboot/program exit jump instruction|
|0x03|byte|unused (would be iobyte)|
|0x04|byte|default drive|
|0x05|3 bytes|syscall jump instruction|
|0x08|120 bytes|interrupts and work area for BIOS|
|0x80|byte|length of command line|
|0x81|127 bytes|command line with $length bytes plus a trailing 0x0D|