83C145 Datasheet, PDF (21/40 Pages) NXP Semiconductors – Microcontrollers for TV and video MTV

Philips Semiconductors
Microcontrollers for TV and video (MTV)
Product specification
83C145; 83C845
83C055; 87C055
Notes to the description of OSAT bits
1. The latches in which the E,SR, D, and Sh bits are captured are cleared to zero at the start of each vertical scan. This
means that if the first text line on the screen is a short row, or if it contains either double size or shadowing, the text
must be preceded by a New Line character. Like all such characters, this initial New Line advances the vertical
screen position; the VStart value (see register OSORG; Section 13.9) should take this fact into account.
2. For SplitBSpace, a change in B and Bcolor occurs halfway through the character horizontally.
3. The normal Space character has no effect on the Bcolor value.
4. The Bcolor value is not cleared between vertical scans, so that if a single background colour is all that is needed in
an application, it can be set via a single BSpace character during program initialization, and never changed
thereafter. In order for such a BSpace to actually affect the 83C055 internal Bcolor register the Mode field of the
OSMOD register must be set to ‘01B’ (or higher) so that the OSD hardware is operating (see register OSMOD;
Section 13.8).
Table 22 OSD outputs related to character bit map value, Fcolor, Bcolor and B bits
CHARACTER BIT MAP VALUE
logic 1
logic 0
VID2
FC2
BC2
OSD OUTPUTS (notes 1 and 2)
VID1
FC1
BC1
VID0
FC0
BC0
VCTRL
driven active
B
Notes
1. Bcolor (BC2,BC1,BC0) values ‘000’ and ‘111’ minimize the occurrence of transient states among the VID2 to VID0
outputs.
2. The background colour defined by the most recently encountered BSpace or SplitBSpace character is maintained
on the VID2 to VID0 pins except at the following times:
a) During the active time of HSYNC.
b) During the active time of VSYNC.
c) During those pixels of an active character that correspond to a logic 1 in the character’s bit map.
d) During a ‘shadow’ bit.
1996 Mar 22
21