Panasonic JB-3300 Technical Manual page 200

(1) First converter
The first converter converts 8-bit data (LCHG7 to LCHGO) to
4-bit data. First, the upper 4 bits (LCHG7 to LCHG4) are sent,
followed by the lower 4 bits (LCHG3 to LCHGO). Switching
between the upper 4 bits and the lower 4 bits is done by the
CRTC-CLK signal in the TEXT 40x25 display mode, or by the *CLK1
Signal in other display modes. Figure 5-55 shows an operation
timing chart.
o TEXT 40x25 Display Mode
CRTC-CLK | | I | : [
LCHG7 to 0 xX LCHG (n) \ Yo LCHG (n+l)
} /
4 Bit Conver-
sion Data B LCHG(n) Upper bit data x LCHG(n) Lower bit data. XLCHGin+1) Upper bit data x
o Other Display Modes
" Oo ( TF r( L_ | |
LCHG7 to 0 x ' LCHG (n] ; KX - en Xv 5 reer
4 Bit Conver- LCHG(n) Upper LCHG(n) Upper LCHGint!) Upper /LCHG(n+l) Lower \/LCHGin+2) Upper V/LCHG(nt+2) Lower
sion Data bit data bit data bit data bit data bit data it data
Figure 5-55 First Converter Timing Chart
(2) Second converter
The second converter enlarges each bit of 4-bit data, doubling
it for conversion to 8-bit data in the TEXT 40x25 display mode.
In the GRAPHIC 320x200 display mode, it converts the data to dot
patterns according to the dot code (CO, C1) and raster address
RAO.
No data conversion takes place in other display modes. Table
5-5 shows a conversion table.
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