1996 Mar 22

30

Philips Semiconductors

Product specification

Microcontrollers for TV and video (MTV)

83C145; 83C845

83C055; 87C055

15 PROGRAMMING THE OSD EPROM

15.1

Overview

The OSD EPROM space starts at location C000H and

ends at location CFFFH. However, due to the addressing

scheme of the OSD, not all locations within this space are

used.The start location of the next character can be

calculated by adding 40H to the start location of the

previous character. For example, character 1 starts at

C000H; then characters 2, 3, and 4 start at C040H,

C080H, and C0C0H, respectively.

15.2

Character description and programming

An example of an OSD character bit map, and the program

data to obtain that character is shown in Table 34.

Each character is 14 bits wide by 18 lines high.A character

is split about a vertical axis into two sections UPPER and

LOWER as illustrated in Table 34:

• Each section contains 7 bits of the character, such that:

– the LOWER section contains bits 7 to 1, and

– the UPPER section contains bits 14 to 8.

• The LOWER section of the character is programmed

when the LSB of the program address equals a logic 0,

and the UPPER section when the LSB equals a logic 1.

During Programming and Verification, each section is

programmed using bytes of program data. The MSB of the

program data is not used; however, the MSB location

physically exists, and so will Program and Verify.

15.3

OSD EPROM bit map

The mapping for the full OSD EPROM is shown in Table 35. To program the example character into the first character

location of the OSD EPROM would require the data at the address as shown in Table 34.

Table 34 Example of an OSD Character Bit Map (note 1)

Note

1. X can be a logic 0 or logic 1, and will Program and Verify correctly.

LINE

CHARACTER BIT MAP

PROGRAM DATA

ADDRESS (HEX)

UPPER

(BIT 14 TO 8)

LOWER

(BIT 7 TO 1)

UPPER

LOWER

UPPER

LOWER

Line 1

0000000

0000000

X0000000

X0000000

C001

C000

Line 2

0000000

0000000

X0000000

X0000000

C003

C002

Line 3

0011110

0001100

X0011110

X0001100

C005

C004

Line 4

0011110

0001100

X0011110

X0001100

C007

C006

Line 5

0011110

0001100

X0011110

X0001100

C009

C008

Line 6

0011110

0001100

X0011110

X0001100

C00B

C00A

Line 7

0011110

0001100

X0011110

X0001100

C00D

C00C

Line 8

0011110

0001100

X0011110

X0001100

C00F

C00E

Line 9

0011111

1111100

X0011111

X1111100

C011

C010

Line 10

0011111

1111100

X0011111

X1111100

C013

C012

Line 11

0011111

1111100

X0011111

X1111100

C015

C014

Line 12

0011110

0001100

X0011110

X0001100

C017

C016

Line 13

0011110

0001100

X0011110

X0001100

C019

C018

Line 14

0011110

0001100

X0011110

X0001100

C01B

C01A

Line 15

0011110

0001100

X0011110

X0001100

C01D

C01C

Line 16

0011110

0001100

X0011110

X0001100

C01F

C01E

Line 17

0000000

0000000

X0000000

X0000000

C021

C020

Line 18

0000000

0000000

X0000000

X0000000

C023

C022