PCB8517 datasheet(5/24 Pages) PHILIPS

5 / 24 page

1997 Mar 03

Philips Semiconductors

Objective speciﬁcation

Stand-alone OSD for monitor applications

PCB8517

FUNCTIONAL DESCRIPTION

3-wire high speed serial interface (HSSI)

The 3-wire (EN, SDI and SCK) high speed serial interface

of the PCB8517 is write only and is used to write data from

the microcontroller to the internal 273 bytes of RAM (see

Section “Internal RAM organization (see Fig.4)”) to control

the OSD. The RAM is organized into 11 rows of

32 columns (see Fig.4) and can be programmed by three

types of sequence (see Section “Data sequence and

format”).

DATA PROTOCOL

Figure 3 shows the protocol of HSSI. To initiate HSSI

transmission, pin EN must be LOW to enable the

PCB8517 to accept data. The EN input must be pulled

LOW prior to the occurrence of SCK and remain LOW until

after the last SCK clock pulse. The rising edge of SCK

facilitates the input data of SDI being shifted into an 8-bit

shift register. When the shift register is full this data will be

loaded into a row address register, column address

Table 1 shows the switching characteristics when the

HFLB pin has a pulse presented, but when there is no

horizontal sync pulse present on the HFLB pin, the

transmission bit rate will be slowed down to 500 kbit/s.

Table 1

Switching characteristics (under operating

conditions)

SYMBOL

PARAMETER

MIN.

MAX. UNIT

tsu(EN)

EN to SCK set-up time 200

−

th(EN)

EN to SCK hold time

100

−

tSCKL

SCK LOW time

200

−

tSCKH

SCK HIGH time

200

−

tsu(SDI)

SDI data set-up time

200

−

th(SDI)

SDI data hold time

100

−

Fig.3 3-wire serial interface protocol.

handbook, full pagewidth

MSB

first byte

LSB

last byte

tsu(EN)

th(EN)

tSCKL

tSCKH

th(SDI)

tsu(SDI)

SCK

SDI

MGD764

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