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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
1340 of 1441
NXP Semiconductors
UM10503
Chapter 48: 12-bit ADC (ADCHS)
48.6.3 FIFO fill level register
This register reflects the FIFO fill level. If the LEVEL bit field returns 0, either the FIFO is
empty or the FIFO contains 16 words. To determine the true FIFO fill level in this case,
read the FIFO_EMPTY bit in the STATUS0 register (
•
If FIFO_EMPTY = 1, then all data in the FIFO have been read out and the FIFO is
empty.
•
If FIFO_EMPTY = 0, then the FIFO contains 16 words.
Remark:
After issuing a FIFO flush command it takes time to update the FIFO fill level
status register. To read the correct FIFO fill level at least one CPU cycle should be
inserted between a flush command and a FIFO fill level read.
48.6.4 FIFO configuration register
This register configures whether 1 or 2 samples are packed in one FIFO word. The
packed data format.
This register also defines at what FIFO fill level the interrupt flag FIFO_FULL is asserted.
Remark:
The channel ID is optional. This is configured in register CONFIG.
Table 1124.FIFO fill level register (FIFO_STS, address 0x400F 0008) bit description
Bit
Symbol
Description
Reset
value
3:0
LEVEL
0 = FIFO is empty or FIFO level of 16 words has been
reached.
1...15 = FIFO is partially full and contains 1 to 15 words.
0x00
31:4
-
Reserved.
-
Fig 188. FIFO packed data format
“0”
b31
“0”
b30..b2 8
“00 0” o r
chann el ID
b27..b1 6
sample 2n +1
b15
“0”
b 14..b12
b 11..b0
samp le 2n
“00 ..00 ”
samp le
bit
PACKED_READ = 0
1 sample/word
PACKED_READ = 1
2 sa mpl es/word
“000” or
cha nnel ID
“000” or
cha nnel ID
an empt y FIF O r et ur ns 0x8000
Table 1125.FIFO configuration register (FIFO_CFG, address 0x400F 000C) bit description
Bit
Symbol
Description
Reset
value
0
PACKED_READ
0 = one sample is packed in one 32-bit read cycle
1 = two samples are packed in one 32-bit read cycle
0x0
4:1
FIFO_LEVEL
When the FIFO contains more or equal than
FIFO_LEVEL samples, the interrupt flag FIFO_FULL
interrupt will be set and DMA_Read_Req will be raised.
The maximum threshold that can be programmed is 15
words. Note that the FIFO can contain up to 16 words.
0x8
31:5
-
Reserved
-