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Move first half of chapter 6 to root
This commit is contained in:
T. Joseph Carter
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5988223c94
commit
25bdb9698c
@ -1,8 +1,5 @@
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.bp
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.np
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.ce
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CHAPTER 6 - USING DOS FROM ASSEMBLY LANGUAGE
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.sp1
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CAVEAT
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This chapter is aimed at the advanced
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@ -15,7 +12,7 @@ topics covered here may be beyond the
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comprehension (at least for the
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present) of a programmer who has
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never used assembly language.
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.sp2
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DIRECT USE OF DISK DRIVE
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It is often desirable or necessary to
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@ -33,8 +30,7 @@ user written operating system to DOS-independent
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utility programs. The
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device address assignments are given
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in Figure 6.1.
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.sp
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.nf
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ADDRESS LABEL DESCRIPTION
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---------------------------------------------------------------
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$C080 PHASEOFF Stepper motor phase 0 off.
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@ -53,15 +49,14 @@ ADDRESS LABEL DESCRIPTION
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$C08D Q6H Load Data Latch.
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$C08E Q7L Prepare latch for input.
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$C08F Q7H Prepare latch for output.
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.sp1
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Q7L followed by Q6L = Read
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Q7L followed by Q6H = Sense Write Protect
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Q7H followed by Q6L = Write
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Q7H followed by Q6H = Load Write Latch
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.sp1
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*** figure 6.1 ***
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.fi
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.bp
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The addresses are slot dependent and
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the offsets are computed by
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multiplying the slot number by 16.
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@ -87,8 +82,7 @@ be taken to insure that the data will
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be in an appropriate register. All
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of the following would engage drive
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number 1. (Assume slot number 6)
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.sp1
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.nf
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LDA $C0EA
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BIT $C08A,X (where X-reg contains $60)
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CMP $C08A,X (where X-reg contains $60)
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@ -99,7 +93,7 @@ address assignments. For more
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examples, see APPENDIX A. Slot 6 is
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assumed and the X-register contains
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$60.
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.sp1
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STEPPER PHASE OFF/ON:
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Basically, each of the four phases
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@ -114,35 +108,31 @@ recommended that the SEEK command in
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RWTS be used to move the arm. See
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the section on using RWTS immediately
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following.
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.sp1
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MOTOR OFF/ON:
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.sp1
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.nf
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LDA $C088,X Turn motor off.
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.sp1
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LDA $C089,X Turn motor on.
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.sp1
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.fi
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NOTE: A sufficient delay should be
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provided to allow the motor time to
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come up to speed. Shugart recommends
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one second, but DOS is able to reduce
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this delay by watching the read latch
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until data starts to change.
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.bp
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.nf
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ENGAGE DRIVE 1/2:
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.sp1
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LDA $C08A,X Engage drive 1.
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.sp1
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LDA $C08B,X Engage drive 2.
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.sp1
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READ A BYTE:
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.sp1
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READ LDA $C08C,X
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BPL READ
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.sp1
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.fi
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NOTE: $C08E,X must already have been
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accessed to assure Read mode. The
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loop is necessary to assure that the
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@ -150,21 +140,19 @@ accumulator will contain valid data.
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If the data latch does not yet
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contain valid data the high bit will
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be zero.
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.sp1
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.nf
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SENSE WRITE PROTECT:
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.sp1
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LDA $C08D,X
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LDA $C08E,X Sense write protect.
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BMI ERROR If high bit set, protected.
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.sp1
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WRITE LOAD AND WRITE A BYTE
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.sp1
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LDA DATA
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STA $C08D,X Write load.
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ORA $C08C,X Write byte.
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.sp1
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.fi
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NOTE: $C08F,X must already have been
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accessed to insure Write mode and a
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100 microsecond delay should be
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@ -180,8 +168,7 @@ be necessary, depending on how the
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data is to be accessed, and code can
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not cross memory page boundaries
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without an adjustment.
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.bp
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.nf
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LDA #$D5 (3 cycles)
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JSR WRITE9 (6)
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LDA #$AA (3)
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@ -195,7 +182,7 @@ without an adjustment.
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WRITE STA $C08D,X (5)
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ORA $C08C,X (4)
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RTS (6)
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.sp2
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CALLING READ/WRITE TRACK/SECTOR (RWTS)
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Read/Write Track/Sector (RWTS) exists
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@ -238,10 +225,9 @@ calling $3E3 as described above. The
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IOB must contain appropriate
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information as defined in the list
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on the facing page (offsets are given in hexadecimal):
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.bp
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.nf
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INPUT/OUTPUT CONTROL BLOCK - GENERAL FORMAT
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.sp1
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BYTE DESCRIPTION
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00 Table type, must be $01
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01 Slot number times 16 (s0: s=slot. Example: $60)
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@ -270,18 +256,18 @@ BYTE DESCRIPTION
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0E Volume number of last access (must be initialized)
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0F Slot number of last access*16 (must be initialized)
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10 Drive number of last access (must be initialized)
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.sp1
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DEVICE CHARACTERISTICS TABLE
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.sp1
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BYTE DESCRIPTION
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00 Device type (should be $00 for DISK II)
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01 Phases per track (should be $01 for DISK II)
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02-03 Motor on time count (should be $EFD8 for DISK II)
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.bp
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RWTS IOB BY CALL TYPE
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.sp1
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SEEK Move disk arm to desired track
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.sp1
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Input: Byte 00 - Table type ($01)
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01 - Slot number * 16 (s0: s=slot)
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02 - Drive number ($01 or $02)
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@ -290,13 +276,13 @@ Input: Byte 00 - Table type ($01)
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0C - Command code for SEEK ($00)
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0F - Slot number of last access * 16
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10 - Drive number of last access
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.sp1
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Output: Byte 0D - Return code (See previous definition)
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0F - Current Slot number * 16
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10 - Current Drive number
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.sp1
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READ Read a sector into a specified buffer
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.sp1
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Input: Byte 00 - Table type ($01)
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01 - Slot number * 16 (s0: s=slot)
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02 - Drive number ($01 or $02)
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@ -310,14 +296,14 @@ Input: Byte 00 - Table type ($01)
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0E - Volume number of last access
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0F - Slot number of last access * 16
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10 - Drive number of last access
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.sp1
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Output: Byte 0D - Return code (See previous definition)
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0E - Current Volume number
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0F - Current Slot number * 16
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10 - Current Drive number
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.bp
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WRITE Write a sector from a specified buffer
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.sp1
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Input: Byte 00 - Table type ($01)
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01 - Slot number * 16 (s0: s=slot)
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02 - Drive number ($01 or $02)
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@ -331,15 +317,15 @@ Input: Byte 00 - Table type ($01)
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0E - Volume number of last access
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0F - Slot number of last access * 16
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10 - Drive number of last access
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.sp1
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Output: Byte 0D - Return code (See previous definition)
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0E - Current Volume number
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0F - Current Slot number * 16
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10 - Current Drive number
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.sp1
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FORMAT Initialize the diskette (does not put DOS on disk,
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create a VTOC/CATALOG, or store HELLO program)
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.sp1
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Input: Byte 00 - Table type ($01)
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01 - Slot number * 16 (s0: s=slot)
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02 - Drive number ($01 or $02)
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@ -349,10 +335,10 @@ Input: Byte 00 - Table type ($01)
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0E - Volume number of last access
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0F - Slot number of last access * 16
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10 - Drive number of last access
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.sp1
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Output: Byte 0D - Return code (See previous definition)
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0E - Current Volume number
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0F - Current Slot number * 16
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10 - Current Drive number
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.bp
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.nx ch6.2
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