lfn_memcpy.txt

一款MP3 Player Firmware 的原代码,非常有参考价值

Specialized memcpy for long filenames:

Offset	Contents
------	--------
0	-
1	char #1
2	-
3	char #2
4	-
5	char #3
6	-
7	char #4
8	-
9	char #5
10	-
11	(attrib)
12	(type)
13	(cksum)
14	char #6
15	-
16	char #7
17	-
18	char #8
19	-
20	char #9
21	-
22	char #10
23	-
24	char #11
25	-
26	-
27	-
28	char #12
29	-
30	char #13
31	-

config registers:

source addr
count register = 16
dest addr
msb mask   0000000000011111 = 0x001F
lsb mask   1101111110000000 = 0xDF80


operations:

read_16 dram @ src_addr_reg
inc src_addr_reg
inc src_addr_reg
if lsb_mask_reg[0] {
	read_mod_write dram @ dest_addr_reg
	inc dest_addr_reg
}
rotate lsb_mask_reg
if msb_mask_reg[0] {
	read_mod_write dram @ dest_addr_reg
	inc dest_addr_reg
}
rotate msb_mask_reg
dec count_reg
if count_reg == 0 {
	done_flag
}