UPD360 datasheet(77/221 Pages) MICROCHIP

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DS00002084C-page 77

UPD360

Sink establishes connection with Source and a PD contract is negotiated. Sink wants to transmit AMS to Source.

Via the CC Hardware Control Register (CC_HW_CTL), the MATCH_DB_UNITS is set to 1b to utilize 100 us units

for the CC match debouncer. The BLK_PD_MSG bit is set to filter PD traffic from the debouncer.

Software sets the Match Debounce Register (MATCH_DEB) to 400 us by writing four into the register.

Software configures CC_THR4 to enable interrupt assertion via the CCx Match Enable Registers (CCx_-

MATCH_EN).

Software configures CC_THR4 for sampling via the CCx Sample Enable Registers (CCx_SAMP_EN).

Via the CC Control Register (CC_CTL), the CC Comparator Control selects the CC pin connected to the Source’s

Rp.

Software waits for indication that Source’s Rp is SinkTxOK via a match detected on CC_THR4.

Software initiates transmission of PD message to Source.

APPLICATION NOTE: Software must guarantee that a sufficient gap exists in between consecutively transmitted

PD messages to enable the source RP value to settle on the CC line. Studies by USB-IF

members have showed the settling time may take in excess of 40 us.

9.6

Dead Battery

Two variations of the Rd resistor are implemented: Rd (Dead Battery) and Rd (Trimmed). The CC1_DB_EN and CC2_D-

B_EN pins exist to determine the operation of the CC pins in dead battery conditions and are to be connected externally

via the PCB to the respective CC pin. The CC pins are configured to present either Hi-Z or an untrimmed Rd pull-down

resistance when connected to a DFP advertising a pull-up resistance.

Figure 9-1 illustrates the configuration for supporting dead battery cases via hair pining CCx_DB_EN and CCx together

on the PCB. The UFP pull-up activates the FET in series with RD_DB and enables the untrimmed dead battery pull-

down.

Figure 9-2 illustrates operation after the UFP has been powered over VBUS by the DFP. After the device is powered,

EN_RD_DB asserts by default to keep the RD_DB pull-down activated.

Note:

The units of the Match Debounce Register (MATCH_DEB) is determined by MATCH_DB_UNITS bit in CC

Hardware Control Register (CC_HW_CTL). When this bit is clear, the units are 1.6 ms. When this bit is set

the units are 100 us.

FIGURE 9-1:

CC RD (DEAD BATTERY)

CCx

CC_DB_ENx

EN_RD_DB_N

EN_RD_TRIM

Hi-Z

50 M

RD_DB

5.1 K

RD_TRIM

5.1 K

UFP

DFP

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