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More VT100 ROM code annotations

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This commit is contained in:
Jeff Parsons 2016-08-03 17:52:01 -07:00 • committed by Jeff Parsons
commit 5e931dd7b9
1 changed files with 45 additions and 32 deletions
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79
devices/pc8080/rom/vt100/VT100.asm
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@ -3744,48 +3744,60 @@ X1916: dad h ;;
;;
;; Loads address A into NVR address register
;;
X1928: lda X21ae ; Load accumulator from 0x21ae -- (0x42)
X192b: mvi b,0ffh ; B = 0xff
X192d: inr b ; increment B
sui 0ah ; subtract 0x0a from accumulator
jp X192d ; repeat while accumulator is positive
adi 0ah ; add 0x0a to accumulator
;; B = A/10, A = A%10 -- this is almost certainly related to NVR!
;; First, fill the buffer at 21d3 with 20 bytes of 0x23 (accept address 1)
lxi h,X21d3 ; HL = 0x21d3
mvi e,23h ; E = 0x23
mvi d,14h ; D = 0x14
X193c: mov m,e ;
inx h ; HL++
dcr d ; D--
jnz X193c ; repeat until D is zero
;; End buffer with 0x2f -- put in standby
mvi m,2fh ; Store 0x2f in 21e7
;; Set 21d3 + a to 0x22 (accept address 0)
lxi h,X21d3 ; HL = 0x21d3
mov e,a ; copy A to E
mvi d,0 ; clear D
dad d ; add DE to HL -- calculate address of bit A
mvi m,22h ; Store 0x22 in M
;; Set 21d3 + 10 + b to 0x22 (accept address 0)
lxi h,X21d3 ; HL = 0x21d3
mvi a,0ah ; A = 0x0a
add b ; A = 0x0a + B
X1928: lda X21ae ;; Load accumulator from 0x21ae -- (0x42)
X192b: mvi b,0ffh ;; B = 0xff
X192d: inr b ;; increment B
sui 0ah ;; subtract 0x0a from accumulator
jp X192d ;; repeat while accumulator is positive
adi 0ah ;; add 0x0a to accumulator
;; B = A/10, A = A%10 -- this is almost certainly related to NVR!
;; First, fill the buffer at 21d3 with 20 bytes of 0x23 (accept address 1)
lxi h,X21d3 ;; HL = 0x21d3
mvi e,23h ;; E = 0x23
mvi d,14h ;; D = 0x14
X193c: mov m,e ;;
inx h ;; HL++
dcr d ;; D--
jnz X193c ;; repeat until D is zero
;; End buffer with 0x2f -- put in standby
mvi m,2fh ;; Store 0x2f in 21e7
;; Set 21d3 + a to 0x22 (accept address 0)
lxi h,X21d3 ;; HL = 0x21d3
mov e,a ;; copy A to E
mvi d,0 ;; clear D
dad d ;; add DE to HL -- calculate address of bit A
mvi m,22h ;; Store 0x22 in M
;; Set 21d3 + 10 + b to 0x22 (accept address 0)
lxi h,X21d3 ;; HL = 0x21d3
mvi a,0ah ;; A = 0x0a
add b ;; A = 0x0a + B
mov e,a
dad d
mvi m,22h
;; Wait for horiz latch
X1957: in 42h
ana c
jnz X1957
;; Now copy from 21d3 to nvr latch, one per edge, 21 bytes
lxi h,X21d3
mvi b,15h ;
mvi b,15h ;;
X1962: in 42h
ana c ; Flags Buffer & C
ana c ;; Flags Buffer & C
jz X1962
dcr b
rm ; Return if B is negative
rm ;; Return if B is negative
X196a: in 42h
ana c
jnz X196a
@ -4712,6 +4724,8 @@ X1fbd: in 1
X1fd4: ora a
mov a,c
ret
;
; Last but not least, pad out to 8K (8192) bytes
;
nop
nop
@ -4936,7 +4950,6 @@ Xcd0b equ 0cd0bh
Xd0f2 equ 0d0f2h
Xfe1a equ 0fe1ah
Xff01 equ 0ff01h
;
end
;
end