I'm still waiting on the USB to serial adapter for testing the 68hc11 BASIC. I should have ordered from Newegg instead of ebay. But that leaves more time to work on the VZ ROM disassembly.
The goal is to mostly to fully commented VZ ROM disassembly, but up until now I have only thrown in a few comments for things like RST calls.
Below is a little sample of what the disassembly looks like once commends are added.
All function names and comments were added by sed. The comments were extracted from the OCR text of a book for the TRS-80. The formatting could use some work, but it's significant progress. This will result in a fully commented disassembly but with actual labels for system functions and variables that were never in any books. VZ specific code will still need comments, but this will take care of a significant portion of the ROM.
This has involved a lot of data entry, and editing, but the speed at which changes can be made and applied to the entire file is well worth the effort. I should also be able to generate disassemblies of other Z80 machines using Microsoft BASIC much faster if they share system variables and code. The TRS-80 itself should be trivial other than fixing the ROM entry points for the disassembler and moving system variables.
The goal is to mostly to fully commented VZ ROM disassembly, but up until now I have only thrown in a few comments for things like RST calls.
Below is a little sample of what the disassembly looks like once commends are added.
All function names and comments were added by sed. The comments were extracted from the OCR text of a book for the TRS-80. The formatting could use some work, but it's significant progress. This will result in a fully commented disassembly but with actual labels for system functions and variables that were never in any books. VZ specific code will still need comments, but this will take care of a significant portion of the ROM.
This has involved a lot of data entry, and editing, but the speed at which changes can be made and applied to the entire file is well worth the effort. I should also be able to generate disassemblies of other Z80 machines using Microsoft BASIC much faster if they share system variables and code. The TRS-80 itself should be trivial other than fixing the ROM entry points for the disassembler and moving system variables.
07C3: 21 25 79 L07C3: LD HL,SIGN ;--- Reset sign flag so that ************ see note--> *
07C6: 7E LD A,(HL) ;--- mantissa will have a negative sign
07C7: 2F CPL ;--- Invert the sign flag
07C8: 77 LD (HL),A ;--- Store sign flag
07C9: AF XOR A ;--- Zero A
07CA: 6F LD L,A ;--- then save it
07CB: 90 SUB B ;--- Complement B (0 - B)
07CC: 47 LD B,A ;--- Save new value of B
07CD: 7D LD A,L ;--- Reload zero into A
07CE: 9B SBC A,E ;--- Complement E (0 - E)
07CF: 5F LD E,A ;--- Save new value for E
07D0: 7D LD A,L ;--- Reload A with zero
07D1: 9A SBC A,D ;--- Complement D (0 - D)
07D2: 57 LD D,A ;--- Save new D value
07D3: 7D LD A,L ;--- Reload A with zero
07D4: 99 SBC A,C ;--- Complement C (0 - C)
07D5: 4F LD C,A ;--- Save new C value
07D6: C9 RET ;---Rtn to caller *********** Unpack a SP number ******
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