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avr-assembly-play
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Added some comments in the undocumented parts and deleted some unuseful instructions

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lucic71 2020-06-06 13:41:56 +03:00
parent 09efd45646
commit 0025446b12
1 changed files with 24 additions and 42 deletions
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66
7_segment_display/segment.s
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@ -13,15 +13,21 @@
.equ PORTD, 0x0B
.equ DDRD, 0x0A
; Aliases for registers. It is easier to develop the logic this way.
; Aliases for registers. ABIT, BBIT, CBIT, DBIT contain the bits in the binary
; representation of numbers displayed on the 7 segment display. A is the MSB
; and D is the LSB. RESULT, TEMP1 and EOREG are registers used when computing
; the boolean functions for each PIN. PINCONFIG is the register that decides
; which PINs are set when sending voltage to the 7 segment display.
.equiv ABIT, 17
.equiv BBIT, 18
.equiv CBIT, 19
.equiv DBIT, 20
.equiv RESULT, 21
.equiv TEMP1, 22
.equiv EOREG, 23
.equiv PINCONFIG, 30
.org 0x0000
@ -81,14 +87,17 @@ ENCODE:
clr PINCONFIG
clr RESULT
; Output a blank screen to put some delay between digits, it looks smoother
; this way.
out PORTD, PINCONFIG
call WAIT
; Description:
; -----------
;
; To represent a digit we will use a 4 bit number looking like this DCBA
; (A is the LSB and D is the MSB). The equations for the 7 segment display
; To represent a digit we will use a 4 bit number looking like this ABCD
; (A is the MSB and D is the LSB). The equations for the 7 segment display
; PINs are the following, they can be easily computed using Karnaugh
; Diagrams:
;
@ -121,6 +130,12 @@ ENCODE:
asr ABIT
asr ABIT
; After shifting each bit in its corresponding register, clear carry flag
; because we will perform multiple ROL's and don't want any additional
; bit coming from Carry in RESULT.
clc
; EOREG will be used for eor'ing with register TEMP1 or RESULT
; It is equivalent with flipping the bit in TEMP1 or RESULT.
@ -173,7 +188,6 @@ COMPUTEB:
and TEMP1, DBIT
or RESULT, TEMP1
clc
rol RESULT
or PINCONFIG, RESULT
@ -195,10 +209,7 @@ COMPUTEC:
or RESULT, DBIT
clc
rol RESULT
clc
rol RESULT
or PINCONFIG, RESULT
@ -237,13 +248,8 @@ COMPUTED:
and TEMP1, CBIT
or RESULT, TEMP1
clc
rol RESULT
clc
rol RESULT
clc
rol RESULT
or PINCONFIG, RESULT
@ -265,16 +271,9 @@ COMPUTEE:
eor TEMP1, EOREG
or RESULT, TEMP1
clc
rol RESULT
clc
rol RESULT
clc
rol RESULT
clc
rol RESULT
or PINCONFIG, RESULT
@ -306,19 +305,10 @@ COMPUTEF:
and TEMP1, BBIT
or RESULT, TEMP1
clc
rol RESULT
clc
rol RESULT
clc
rol RESULT
clc
rol RESULT
clc
rol RESULT
or PINCONFIG, RESULT
@ -349,22 +339,11 @@ COMPUTEG:
or RESULT, ABIT
clc
rol RESULT
clc
rol RESULT
clc
rol RESULT
clc
rol RESULT
clc
rol RESULT
clc
rol RESULT
or PINCONFIG, RESULT
@ -380,10 +359,13 @@ WAIT:
; Description
; -----------
;
; Loop 0x400000 times which takes approximately 12 milion cycles which is
; approximately 0.7s.
; Loop 0x{r17, r18, r19} times (for example 0x300000) times because the
; internal clock of the board is to fast and the digits cannot be seen.
; We know that 0x400000 iterations take approximately 0.7s so we can make
; further calcualtions based on this (or by looking in the instruction set
; at the clock cycles taken by each instruction used in the loop).
ldi r17, 0x20
ldi r17, 0x30
ldi r18, 0x00
ldi r19, 0x00