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Serial Boot Facility (SBF)
Freescale Semiconductor
12-3
12.3.1
Serial Boot Facility Status Register (SBFSR)
The read-only SBFSR register reflects the amount of boot code loaded through the external SPI memory.
12.3.2
Serial Boot Facility Control Register (SBFCR)
The read-always/write-once SBFCR register controls SBF operation following subsequent warm resets.
Address: 0xFC0A_0018 (SBFSR)
Access: User read-only
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
BLL
W
Reset
See Note
Note:
Reset value is user-defined (loaded from SPI memory during serial boot following any reset type)
Figure 12-2. Serial Boot Facility Status Register (SBFSR)
Table 12-3. SBFSR Field Descriptions
Field
Description
15–0
BLL
Boot load length. Reflects the number of longwords of boot code loaded from external SPI memory during serial
boot. No boot code was loaded if BLL equals 0x0000. Otherwise, BLL plus 1 longwords were loaded.
Address: 0xFC0A_0020 (SBFCR)
Access: User read/write-once
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
0
0
0
0
0
0
0
0
0
0
0
FR
BLDIV
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
See Note
1
Reset value is 0 and is reset only by power-on reset (remains unchanged for other reset types)
Note:
The reset value is loaded from SPI memory during serial boot following power-on reset. It remains unchanged
for other reset types. Prior to this register being loaded from SPI memory, a divisor of 67 is used to begin the
serial boot sequence.
Figure 12-3. Serial Boot Facility Control Register (SBFCR)
Table 12-4. SBFCR Field Descriptions
Field
Description
15–5
Reserved, must be cleared.
4
FR
Fast read. Determines whether the SBF uses the standard
READ
command or flash FAST_READ command on
reboot following any reset other than power-on reset. Because this register is write-once, the application must write
the value for this bit in the same write that the BLDIV field is written. Any subsequent writes to this field prior to a
power-on reset event terminate without effect.
0 SBF uses the standard
READ
command
1 SBF uses the FAST_READ command
Содержание MCF54455
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