read.3rd

Old Tarbell CP/M Source Codes

	DEBLOCK SOURCE FILES			4-9-81

   THIS DEBLOCKED BIOS IS IN Z-80 CODE ONLY.
-----------------------------------------------

	This letter describes the files contained on this disk pertaining
	to the use of the deblock software.


1.	512FMT.COM - This formats a disk with track 0 = 26 , 128 byte
	sectors, and tracks 1 to 76 with 16 , 512 byte sectors double
	density. The auto-density byte is automatically placed into
	location 7E hex of sector 1 on track 0. This byte is a DE hex,
	which means deblocked operation to the operating system. Double
	sided formatting is also included in this format program. Double
	sided drives yield approx. 1.2 Mbytes per drive.

2.	512DT.COM - This program test a disk formatted with 512FMT.COM
	and has the same arguements as the other double density test we
	use.

3.	512SGEN.COM - This program is the 512 byte sector sysgen program.
	This program functions just the same as the normal CPM sysgen
	program with the exception that 512sgen may be used in submit
	files as all console input for 512sgen uses CPM function 10.
	This program will automatically write side 1 of a double sided
	disk if told to do so. In a double sided formatted disk, track
	1 of the operating system is in double density.

4.	DBBIOS.ASM - This is the deblocked bios for the Tarbell Double
	Density Disk Controller board. You will have to put your own
	I/O routines and any other changes you need into this bios your-
	self. The I/O as it exist is set up for the Tarbell Z-80 CPU
	board.The MSIZE equ must be set for 1 Kbytes lower than normal,
	as this	bios uses a deblock mechanism which requires more memory
	space than a normal CPM 2.2 uses.
	This bios now supports double sided, double density, deblocked
	operation. It will also read single density, double sided,
	double density single sided (51 x 128), and double density, double
	sided (51 x 128) disks. This bios will read/write any disk format
	produced by Tarbell Electronics.

5.	DMABOOT.ASM - This is a bootstrap loader file used to load the DBBIOS
        file during a reset. If DMA is set to false data transfer with this 
        file is program data transfer and requires that you have a Z-80
        running at 4 MHz to use it. If DMA is set to true It may be used by
        systems which are running 2 MHz Z-80's to load the system into memory.
        It may be used with 4 MHz Z-80's also.

6.	PMPATCH.ASM & PMPATCH.HEX - Patch for CP/M 2.2 to enable building
        page size CP/M's. The bios on this disk is setup for a 63k size so
        the numper of pages for PGMOV is 252.

7.	MACRO.LIB, SKEW.LIB - These two files are necessary if you are
	going to make any changes to the 512DT.ASM file, as they are
	needed to re-assemble this file.

8.	Z80.LIB - This file may be used with Digital Research MAC assembler
	instead of using the ZASM.COM file included on the disk. Be sure
	to set MAC = to TRUE in both the DBBIOS.ASM and DMABOOT.ASM files.
	Otherwise, leave them set to FALSE if you will be using the ZASM.COM
	assembler.

9.	ZASM.COM - This is an assembler which runs on an 8080, but will
	assemble Z-80 code. The DBBIOS and DMABOOT files will need to be
	assembled using this program if you do not have the MAC macro
	assembler.

	You build your operating system just as you would for a normal
	CPM 2.2 configuration by editing the DBBIOS and DMABOOT files with
	your changes. Then assemble them. Remember to creat a CPMxx.COM file
	which is 1 Kbytes lower in memory. eg. CPM 63 *
	After you have saved the memory imiage of the CPM63.COM, bring it
	in using DDT just as normal. Overlay the bios and boot file using
	a relocation value 1 kbyte higher than normal (400 hex), for the
	bios.  e.g. R2980 for a 63K CPM.
	The boot always goes at 900 hex by using R900 as a relocation.
	Then, exit back to CPM by doing a ^C or G0.
	Now bring in the 512SGEN program, and place your 512 byte formatted
	disk into any drive, and tell 512SGEN which drive it's on. It
	will then write the operating system onto that drive.
	At this point, you should be able to boot up on this disk and be
	running deblocked 512 byte sectors.

10.	If you were successful, you may now transfer all your files by placing
	your single density disk with system files into drive b and use PIP.