VP5313/VP5513

11

Figure 5 REC 656 interface with HS output timing

Pixel Data Input (PD[7,0])

PXCK Input (27MHz)

Cb0

Cr0

Y0

Y1

Y2

Y3

Cb1

Cr1

HS

Nck=0

Nck=2

The horizontal line duration for PAL equates to 1728

CLK27M cycles and within each line there are 444 data bit

periods. The duration of 37 data bits (the smallest number

possible for an integer number of CLK27M cycles) therefore

equates to 144 CLK27M cycles.

To ensure that the average bit rate is 6.9375 MHz, 33 in

every 37 data bits will have a duration of 4 CLK27M cycles and

4 in every 37 data bits will have a duration of 3 CLK27M cycles.

Of the first 37 data bits in each line, bits 10, 19, 28 and 37 will

have a duration of 3 CLK27M cycles. The sequence will be

repeated for all subsequent 37 bit groups.

Master Reset

The VP5313/VP5513 must be initialised with RESET. This

is an asynchronous, active low signal and must be active for

a minimum of 200ns in order to reset the VP5313/VP5513.

The device resets to line 64, start of horizontal sync (i.e. line

blanking active). There is no on-chip power on reset circuitry.

(d) = default

xx = don’t care.

The calculation of the FREQ register value is according to the following formula:-

NTSC value is rounded UP from the decimal number. PAL-B, D, G, H, I and N (Argentina) are rounded DOWN. The SC_ADJ

value is derived from the adjustment needed to be added after 8 fields to ensure accuracy of the Subcarrier frequency. Note the

SC_ADJ value of 9C required for PAL-B, D, G, H, I.

Standard

NTSC

PAL-B, G, H, I (d)

PAL-N (Argentina)

FREQ2-0

registers hex

87 C1 F1

A8 26 2B

87 DA 51

Lines/

field

525

625

625

Field

freq. HZ

59.94

50

50

1716

1728

1728

Number of

pixels/line

at 27MHz

15.734266

15.625000

15.625000

Horizontal

freq. kHz.

3.57954545

4.43361875

3.58205625

Subcarrier

freq. kHz.

(455/2)

(1135/4+1/625)

(917/4+1/625)

SC_ADJ

register

hex

xx

9C

57

Table.2 Line, field and subcarrier standards and register settings

NCO Adjustment

12

3

456

7

8

9 10 11 12 13 14 15 16

18

17

19 20 21

22 23 24

434

434

TTXDD

textbit #:

TTX_REQ

TTX_DATA

CVBS/Y

Figure 4 Teletext timing diagram