mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 623

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

Reset
28.2.1 CRC Data Register (CRC_CRC)
The CRC data register contains the value of the seed, data, and checksum. When the
CTRL[WAS] bit is set, any write to the data register is regarded as the seed value. When
the CTRL[WAS] bit is cleared, any write to the data register is regarded as data for
general CRC computation.
In 16-bit CRC mode, the HU and HL fields are not used for programming the seed value,
and reads of these fields return an indeterminate value. In 32-bit CRC mode, all fields are
used for programming the seed value.
When programming data values, the values can be written 8 bits, 16 bits, or 32 bits at a
time, provided all bytes are contiguous.
After all data values are written, the CRC result can be read from this data register. In 16-
bit CRC mode, the CRC result is available in the LU and LL fields. In 32-bit CRC mode,
all fields contain the result. Reads of this register at any time return the intermediate CRC
value, provided the CRC module is configured.
Address: CRC_CRC is FFFF_8570h base + 0h offset = FFFF_8570h
Freescale Semiconductor, Inc.
Bit
W
R
FFFF_8578
Absolute
address
(hex)
31
1
31–24
23–16
Field
HU
HL
30
1
29
1
CRC Control Register (CRC_CTRL)
28
1
HU
CRC High Upper Byte
In 16-bit CRC mode (the CTRL[TCRC] bit is 0), this field is not used for programming a seed value. In 32-
bit CRC mode (the CTRL[TCRC] bit is 1), values written to this field are part of the seed value when the
CTRL[WAS] bit is 1. When the CTRL[WAS] bit is 0, data written to this field is used for CRC checksum
generation in both 16-bit and 32-bit CRC modes.
CRC High Lower Byte
In 16-bit CRC mode (the CTRL[TCRC] bit is 0), this field is not used for programming a seed value. In 32-
bit CRC mode (the CTRL[TCRC] bit is 1), values written to this field are part of the seed value when the
27
1
26
1
25
1
24
1
MCF51JF128 Reference Manual, Rev. 2, 03/2011
23
1
Register name
22
1
CRC memory map (continued)
CRC_CRC field descriptions
21
1
Table continues on the next page...
20
1
HL
19
1
18
1
Preliminary
17
1
16
1
15
1
Description
14
1
13
1
12
1
(in bits)
Chapter 28 Cyclic Redundancy Check (CRC)
Width
LU
16
11
1
10
1
Access
1
9
R/W
1
8
1
7
Reset value
1
6
0000h
1
5
4
1
LL
1
3
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28.2.3/
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