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cmp.rst

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cmp command

Synopsis

cmp [.b, .w, .l, .q] addr1 addr2 count

Description

The cmp command is used to compare two memory areas. By default it works on four byte (32-bit) values. By appending .b, .w, .l, .q the size of the values is controlled:

cmp.b
compare 1 byte (8-bit) values
cmp.w
compare 2 byte (16-bit) values
cmp.l
compare 4 byte (32-bit) values
cmp.q
compare 8 byte (64-bit) values

The parameters are used as follows:

addr1
Address of the first memory area.
addr2
Address of the second memory area.
count
Number of bytes to compare (as hexadecimal number).

Example

In the example below the strings "Hello worldn" and "Hello Worldn" are written to memory and then compared.

=> mm.b 0x1000000
01000000: 00 ? 48
01000001: 00 ? 65
01000002: 00 ? 6c
01000003: 00 ? 6c
01000004: 00 ? 6f
01000005: 00 ? 20
01000006: 00 ? 77
01000007: 00 ? 6f
01000008: 00 ? 72
01000009: 00 ? 6c
0100000a: 00 ? 64
0100000b: 00 ? 0d
0100000c: 00 ? => <INTERRUPT>
=> mm.b 0x101000
00101000: 00 ? 48
00101001: 00 ? 65
00101002: 00 ? 6c
00101003: 00 ? 6c
00101004: 00 ? 6f
00101005: 00 ? 20
00101006: 00 ? 57
00101007: 00 ? 6f
00101008: 00 ? 72
00101009: 00 ? 6c
0010100a: 00 ? 64
0010100b: 00 ? 0d
0010100c: 00 ? => <INTERRUPT>
=> cmp 0x1000000 0x101000 0xc
word at 0x01000004 (0x6f77206f) != word at 0x00101004 (0x6f57206f)
Total of 1 word(s) were the same
=> cmp.b 0x1000000 0x101000 0xc
byte at 0x01000006 (0x77) != byte at 0x00101006 (0x57)
Total of 6 byte(s) were the same
=> cmp.w 0x1000000 0x101000 0xc
halfword at 0x01000006 (0x6f77) != halfword at 0x00101006 (0x6f57)
Total of 3 halfword(s) were the same
=> cmp.l 0x1000000 0x101000 0xc
word at 0x01000004 (0x6f77206f) != word at 0x00101004 (0x6f57206f)
Total of 1 word(s) were the same
=> cmp.q 0x1000000 0x101000 0xc
double word at 0x01000000 (0x6f77206f6c6c6548) != double word at 0x00101000 (0x6f57206f6c6c6548)
Total of 0 double word(s) were the same

Configuration

The cmp command is only available if CONFIG_CMD_MEMORY=y. The cmp.q command is only available if additionally CONFIG_MEM_SUPPORT_64BIT_DATA=y.

Return value

The return value $? is true (0) if the compared memory areas are equal. The reutrn value is false (1) if the compared memory areas differ.