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UART Registers
1637
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Universal Asynchronous Receiver/Transmitter (UART)
26.5.4 UARTILPR Register (Offset = 0x20) [reset = 0x0]
UART IrDA Low-Power Register (UARTILPR)
The UARTILPR register stores the 8-bit low-power counter divisor value used to derive the low-power SIR
pulse width clock by dividing down the system clock (SysClk). All the bits are cleared when reset.
The internal IrLPBaud16 clock is generated by dividing down SysClk according to the low-power divisor
value written to UARTILPR. The duration of SIR pulses generated when low-power mode is enabled is
three times the period of the IrLPBaud16 clock. The low-power divisor value is calculated as follows:
ILPDVSR = SysClk / F
IrLPBaud16
where F
IrLPBaud16
is nominally 1.8432 MHz.
Because the IrLPBaud16 clock is used to sample transmitted data irrespective of mode, the ILPDVSR
field must be programmed in both low power and normal mode,such that 1.42 MHz < F
IrLPBaud16
< 2.12
MHz, resulting in a low-power pulse duration of 1.41-2.11 us (three times the period of IrLPBaud16). The
minimum frequency of IrLPBaud16 ensures that pulses less than one period of IrLPBaud16 are rejected,
but pulses greater than 1.4 us are accepted as valid pulses.
NOTE:
Zero is an illegal value. Programming a zero value results in no IrLPBaud16 pulses being
generated.
UARTILPR is shown in
and described in
Return to
Figure 26-7. UARTILPR Register
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
RESERVED
ILPDVSR
R-0x0
R/W-0x0
Table 26-7. UARTILPR Register Field Descriptions
Bit
Field
Type
Reset
Description
31-8
RESERVED
R
0x0
7-0
ILPDVSR
R/W
0x0
IrDA Low-Power Divisor.
This field contains the
8-bit low-power divisor value.