Memunpk.asm - Revision history

Mr z: Protected "Memunpk.asm" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

2010-12-04T08:57:23Z

Protected "Memunpk.asm" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

Mr z: /* Notes */

2008-09-07T09:17:56Z

‎Notes

Mr z at 09:16, 7 September 2008

2008-09-07T09:16:25Z

Mr z at 09:13, 7 September 2008

2008-09-07T09:13:36Z

New page

[[Category:Programming]] [[Category:Library]]

= Functions Provided =

<CENTER><TABLE BORDER><TR><TH>Entry point</TH><TH>Function provided</TH><TH>Notes</TH></TR>
<TR><TD>MEMUNPK</TD><TD ROWSPAN=2>Copy a block of memory</TD><TD>Source, destination and length fixed in ROM.</TD></TR>
<TR><TD>MEMUNPK.1</TD><TD>Source, destination and length in registers.</TD></TR></TABLE></CENTER>
<br /><br />
See source code below for calling convention.<br /><br />

= Examples =

(todo... please contribute!)

= Notes =

= Source Code =

<pre>
;* ======================================================================== *;
;* These routines are placed into the public domain by their author. All *;
;* copyright rights are hereby relinquished on the routines and data in *;
;* this file. -- Joseph Zbiciak, 2008 *;
;* ======================================================================== *;

;; ======================================================================== ;;
;; MEMUNPK Unpack a 16-bit array to an 8-bit array. ;;
;; MEMUNPK.1 Alternate entry point ;;
;; ;;
;; AUTHOR ;;
;; Joseph Zbiciak <intvnut AT gmail.com> ;;
;; ;;
;; REVISION HISTORY ;;
;; 08-Sep-2001 Initial Revision ;;
;; ;;
;; INPUTS for MEMUNPK ;;
;; R5 Pointer to invocation record, followed by return address. ;;
;; Pointer to destination 1 DECLE ;;
;; Pointer to source 1 DECLE ;;
;; Length of source array 1 DECLE ;;
;; ;;
;; INPUTS for MEMUNPK.1 ;;
;; R5 Return address ;;
;; R4 Pointer to destination ;;
;; R1 Pointer to source ;;
;; R0 Length of source array ;;
;; ;;
;; OUTPUTS ;;
;; R0 $FFFF ;;
;; R1 Last 16-bit word copied, byte-swapped. ;;
;; R4 Points one element beyond destination array ;;
;; R5 Points one element beyond source array ;;
;; ;;
;; TECHNIQUES ;;
;; Unrolled 4x for speed. ;;
;; Special dispatch handles length % 4 != 0. ;;
;; ;;
;; CODESIZE ;;
;; ?? words ;;
;; ;;
;; CYCLES ;;
;; Not yet characterized. ;;
;; ======================================================================== ;;
MEMUNPK PROC

MVI@ R5, R4 ; 8 Destination array
MVI@ R5, R1 ; 8 Source array
MVI@ R5, R0 ; 8 Length

@@1: PSHR R5 ; 9 Alternate entry point

MOVR R1, R5 ; 6 Use auto-incr pointer

MOVR R0, R1 ; 6 Copy array length
SLR R0, 2 ; 8 Find floor(length / 4)
ANDI #3, R1 ; 8 \
SLL R1, 2 ; 8 |__ Find address to jump to for
SUBI #@@end, R1 ; 8 | first iteration, to handle
NEGR R1 ; 6 / length % 4.
MOVR R1, PC ; 6 Jump into copy loop.

@@loop: MVI@ R5, R1 ; 8 \
MVO@ R1, R4 ; 9 |__ Copy first pair of bytes
SWAP R1, 1 ; 6 |
MVO@ R1, R4 ; 9 /
MVI@ R5, R1 ; 8 \
MVO@ R1, R4 ; 9 |__ Copy second pair of bytes
SWAP R1, 1 ; 6 |
MVO@ R1, R4 ; 9 /
MVI@ R5, R1 ; 8 \
MVO@ R1, R4 ; 9 |__ Copy third pair of bytes
SWAP R1, 1 ; 6 |
MVO@ R1, R4 ; 9 /
MVI@ R5, R1 ; 8 \
MVO@ R1, R4 ; 9 |__ Copy fourth pair of bytes
SWAP R1, 1 ; 6 |
MVO@ R1, R4 ; 9 /

@@end: DECR R0 ; 6
BPL @@loop ; 9/7 Iterate floor(length/4) + 1 times
;----
; 143*k - 2

@@done: PULR PC ; 11 Return
ENDP

;; ======================================================================== ;;
;; End of File: memunpk.asm ;;
;; ======================================================================== ;;
</pre>

← Older revision		Revision as of 09:17, 7 September 2008
Line 14:		Line 14:

	= Notes =		= Notes =
		+
		+	The code expects to write the data in 8-bit memory, such as [[Scratchpad RAM]] or [[Graphics RAM]], and so does not explicitly mask the written value. Instead, it relies on the hardware ignoring the upper 8 bits of the write. This works as expected when writing to 8-bit RAM, which is its intended use.

	= Source Code =		= Source Code =

← Older revision	Revision as of 08:57, 4 December 2010
(No difference)

@@ Line 4: / Line 4: @@
 <CENTER><TABLE BORDER><TR><TH>Entry point</TH><TH>Function provided</TH><TH>Notes</TH></TR>
-<TR><TD>MEMUNPK</TD><TD ROWSPAN=2>Copy a block of memory</TD><TD>Source, destination and length fixed in ROM.</TD></TR>
+<TR><TD>MEMUNPK</TD><TD ROWSPAN=2>Like [[memcpy.asm]], but unpacks 8-bit data stored in 16-bit words</TD><TD>Source, destination and length fixed in ROM.</TD></TR>
 <TR><TD>MEMUNPK.1</TD><TD>Source, destination and length in registers.</TD></TR></TABLE></CENTER>
 <br /><br />