Technical Reference Manual
002-29852 Rev. *B
28.4.1.1.9 TCPWM_GRP_CNT_PERIOD_BUFF
Description:
Counter buffered period register
Address:
0x40380024
Offset:
0x24
Retention:
Retained
IsDeepSleep:
No
Comment:
Default:
0xFFFFFFFF
Bit-field Table
Bits
7
6
5
4
3
2
1
0
Name
PERIOD [7:0]
Bits
15
14
13
12
11
10
9
8
Name
PERIOD [15:8]
Bits
23
22
21
20
19
18
17
16
Name
PERIOD [23:16]
Bits
31
30
29
28
27
26
25
24
Name
PERIOD [31:24]
Bit-fields
Bits Name
SW
HW
Default or
Enum
Description
0:31
PERIOD
RW
RW
429496729
5
Additional buffer for counter PERIOD register.
In PWM_PR mode PEROD_BUFF defines the LFSR
polynomial. Each bit represents a tap of the shift
register which can be feed back to the MSB via an
XOR tree.
Examples for GRP_CNT_WIDTH = 16:
- Maximum length 16bit LFSR
- polynomial x^16 + x^14 + x^13 + x^11 + 1
- taps 0,2,3,5 -> PERIOD = 0x002d
- period is 2^16-1 = 65535 cycles
- Maximum length 8bit LFSR:
- polynomial x^8 + x^6 + x^5 + x^4 + 1
- taps 8,10,11,12 (realized in 8 MSBs of 16bit LFSR)
- period is 2^8-1 = 255 cycles
In SR mode PERIOD_BUFF defines which tap of the
shift register generates the PWM output signals. For a
delay of n cycles (from capture event to PWM output)
the bit CNT_WIDTH-n should be set to '1'. For a shift
register function only one tap should be use, i.e. a one-
hot value must be written to PERIOD_BUFF. If multiple
bits in PERIOD_BUFF are set then the taps are XOR
combined.
1804
2022-04-18
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