Panasonic JB-3300 Technical Manual page 195

(2)
CHG font data latch circuit
In the TEXT display mode, the CHG font data latch circuit converts
the character code on data bus lines CHBO to CHB7 into individual
font data and latches the converted data. The data is latched at the
rising edge of the *CRTC-CLK signal, and output to LCHGO to LCHG7.
Figure 5-50 shows a CHG font data latch circuit.
+5V
(CHB?
CHBG
CHB5
LS374
CHB4 7
(6-108) <cHB3 ;
CHB2 D
CHB I D
CHBO D
(5- 5E) RAB 5
(5-56) RA2 D
(S-5E) RAI
(5- 5D) RAO
(5-5F) GRAPHIC
(6-76) XCRTC-CLK 2
Figure 5-50 CHG Font Data Latch Circuit
The CHG (character generator) has two fonts, Single font and bold
font, each consisting of characters in an 8-dot x 16-dot character
Matrix. The single font and boid font are switched by the foreground
intensity bit (AT3) of the attribute code. The single font is
selected by AT3 = 0, and the bold font by AT3 = l.
Connecting jumper J6 to BO allows the bold font to be selected (AT3 =
1), and connecting it to NO inhibits the bold font. Jumper J6 is
connected to BO when shipped from the factory.
Short plugs J7 and J8 allow selection of either the 28-pin EP-ROM or
the 24-pin mask ROM for the CHG. Connect them to EP to select
EP-ROM, or to MS to select 24-pin mask ROM.
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