STWBC2-HP datasheet(30/96 Pages) STMICROELECTRONICS

30 / 96 page

Figure 34. FSK bit streaming overview

The WPC-Qi fixes the duration of a symbol to 256 cycles of PWM.

The HR-PWM manages FSK function using a FIFO of 72 symbols. The FIFO is filled with symbols by writing

FSK_FIFO_DATA register (8 symbols written per access). When FSK is enabled using the bit FSK_EN of the

PWM_CONTROL_1 register and the FSK FIFO is not empty, the HR-PWM gets bits from FIFO and assigns the

FSK signal accordingly.

The bit rate of FIFO data sent is configured in the FSK_SYMBOL_DURATION registers. The value corresponds to

bit rate counted in number of PWM cycles. A PWM cycle corresponds to a list of steps rollover.

For WPC-Qi compliant FSK, FSK_SYMBOL_DURATION is set to 256. The FIFO can be flushed by setting

the bit FLUSH_FSK_FIFO in the PWM_CONTROL_2 register. The PWM_STATUS register gives FIFO status

information: FSK_FIFO_EMPTY, FSK_FIFO_FULL and FSK_FIFO_HALF_FULL bits.

The FSK_FIFO_HALF_FULL passes 1 if the quantity of symbols in the FIFO is strictly above 36. This

information is useful to reload the FIFO in case of message occupying more than 72 symbols. In fact, since

FSK_FIFO_HALF_FULL is 0, it is certain that 36 symbols can be written in the FIFO. Because of 8bits mapping, it

is certain that 4 writes to FSK_FIFO_DATA register can be done (so 32 symbols).

The FSK functionality requires the following configuration steps:

Configure the duration of a symbol in FSK_SYMBOL_DURATION (256 for WPC-Qi).

Upload up to 72 symbols in the FSK FIFO by writing FSK_FIFO_DATA (8 symbols per write).

Enable the FSK function by setting 1 the bit FSK_EN in the PWM_CONTROL_1 register.

The FSK function drains the FIFO at the configured rate.

While some symbols have not been pushed in the FIFO:

Wait for FSK_FIFO_HALF_FULL passing 0.

Write up to 32 symbols in FSK_FIFO_DATA (4 writes).

Wait for FSK_FIFO_EMPTY passing 1. That signals that message has been sent.

Disable the FSK by writing 0 in FSK_EN bit.

It is possible to let FSK_EN always be 1. In this case, the FSK starts since a write is done in the FSK_FIFO_DATA

one.

2.2.1.4.3

Chronometer configuration

The HR-PWM includes a chronometer function that allows measuring time elapsed between the start of PWM

period (so when list of steps rolls over) and a HW event. The HW event can be chosen by programming the field

EXT_EVENT_SEL in the PWM_CONTROL_1 register:

Quarter wave of LC ringing node

Inverse of quarter wave of LC ringing node

Zero crossing of bridge current

Inverse of zero crossing of bridge current

Zero crossing of LC ringing node

Inverse of zero crossing of LC ringing node

pwm_output[3]

Inverse of pwm_output[3]

STWBC2-HP

Digital AFE functions

DS13825 - Rev 1.0

page 30/96

STWBC2-HP датащи(PDF) 30 Page - STMicroelectronics

STWBC2-HP датащи(HTML) 30 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96

датащи скачать

ссылки URL