Guard Time And Prescaler Register (Usart_Gtpr) - ST STM32F101 Series Reference Manual

Universal synchronous asynchronous receiver transmitter (USART)
19.5.7

Guard time and prescaler register (USART_GTPR)

Address offset: 0x18
Reset value: 0x0000
31 30 29
15 14 13
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Bits 31:16 Reserved, forced by hardware to 0.
Bits 15:8 GT[7:0]: Guard time value.
This bit-field gives the Guard time value in terms of number of baud clocks.
This is used in Smartcard mode. The Transmission Complete flag is set after this guard time value.
Bits 7:0 PSC[7:0]: Prescaler value.
– In IrDA Low-power mode:
PSC[7:0] = IrDA Low-Power Baud Rate
Used for programming the prescaler for dividing the system clock to achieve the low-power
frequency:
The source clock is divided by the value given in the register (8 significant bits):
00000000: Reserved - do not program this value
00000001: divides the source clock by 1
00000010: divides the source clock by 2
...
– In normal IrDA mode: PSC must be set to 00000001.
– In smartcard mode:
PSC[4:0]: Prescaler value.
Used for programming the prescaler for dividing the system clock to provide the smartcard clock.
The value given in the register (5 significant bits) is multiplied by 2 to give the division factor of the
source clock frequency:
00000: Reserved - do not program this value
00001: divides the source clock by 2
00010: divides the source clock by 4
00011: divides the source clock by 6
...
Note: Bits [7:5] have no effect if Smartcard mode is used.
466/501
28 27 26 25
12 11 10 9
GT[7:0]
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24 23 22 21
Reserved
8 7 6 5
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20 19 18 17
4 3 2 1
PSC[7:0]
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RM0008
16
0
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