UPD360 datasheet(167/221 Pages) MICROCHIP

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 2016-2017 Microchip Technology Inc.

DS00002084C-page 167

UPD360

11.4.4.11

BMC TX Bit-Time Count Register (BMC_TX_BITTIME_CNT)

11.4.4.12

BMC Transition Window Time Register (BMC_TRANSITION_WINDOW_TIME)

The value of this register is used by the BMC decoder to determine when the line is IDLE. Detection is active when 3

transitions occur at the receiver within a time window of BMC_TRANSITION_WINDOW_TIME. After waiting

BMC_TRANSITION_WINDOW_TIME without detecting 3 transitions, the bus is considered idle. The USB PD Specifi-

cation calls for 12uS minimum and 20uS maximum.

Address:

1AB0h

Size:

8 bits

Bits

Description

Type

Default

7:0

BMC_TX_BIT_TIME_CNT

Bit-time counter value. The BMC encoder uses this value to determine the bit-

timing for the last bit of data. This register can be used to adjust bit-time for

testing purpose (adjusting bitrate).

Count value is based on clock frequency and is given by:

((Clock Freq KHz / Bit Rate Kbps) - 1)

i.e.,

Clock Frequency = 48000KHz (48MHz)

Nominal Bit Rate = 300 Kbps

bit_time_cnt = (48000 / 300) - 1 = 159

Note:

A value of 159 (decimal) is recommended for this field.

R/W

00h

Address:

1AB1h

Size:

8 bits

Bits

Description

Type

Default

7:0

BMC_TRANSITION_WINDOW_TIME

Time in clock cycles x 4

transition time uS = (BMC_TRANSITION WINDOW_TIME x 4) / clock_freq

MHz

Per the USB PD Specification, this value should be set between 12uS and

20uS. This would be a value between 144 and 240 at 48MHz.

Note:

Unlike the TX Turnaround Time Register (TX_TA_TIME), this hard-

ware does not use a pre-scaler, therefore the time specified is

accurate.

Note:

A value of 200 (decimal) is recommended for this field.

R/W

00h

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