Hitachi HD64411 Q2 User Manual page 176

Therefore, when the Q2 fetches data in the UGM into a buffer, it performs buffer updating by
managing the read destination address of each buffer.
An outline of buffer updating is given in (d) to (f) below.
(d) When the Q2 uses the command buffer, the buffer contents are updated each time the UGM
address value indicated by the Q2 exceeds a 16-word boundary.
(e) When the Q2 uses the source buffer, the buffer contents are updated each time the UGM address
value indicated by the Q2 exceeds a 16-word boundary.
(f) When the Q2 uses the work buffer, the buffer contents are updated each time the UGM address
value indicated by the Q2 exceeds a 4-word boundary.
Problems: The following problems occur depending on the commands used.
(a) When using the POLYGON4B, PLINE, and RPLINE commands
If a binary source within a 16-word boundary is used without updating command parameters
SOURCE ADDRESSH and SOURCE ADDRESSL, the source buffer is not updated since the
address indicated by the Q2 does not exceed a 16-word boundary. In a drawing operation,
drawing is performed using the binary source stored in the source buffer.
(b) When using the POLYGON4A command
If a multi-valued source within a 16-word boundary is used without updating command
parameters TXS and TYS or the source area start address, the source buffer is not updated since
the address indicated by the Q2 does not exceed a 16-word boundary. In a drawing operation,
drawing is performed using the multi-valued source stored in the source buffer.
(c) When using the FTRAP, RFTRAP, CLRW, LINEW, and RLINEW commands
If a binary source within a 4-word boundary is used without updating the work area start
address, the work buffer is not updated since the address indicated by the Q2 does not exceed a
4-word boundary. In a drawing operation, drawing is performed using the work data stored in
the work buffer.
Permanent Remedy: As a method of updating the source buffer contents, either use a source
pattern that exceeds 16 words or use a source pattern at a location that exceeds a 16-word boundary.
As a method of updating the work buffer, either use a work pattern that exceeds 4 words or use a
work pattern at a location that exceeds a 16-word boundary.
6 . 1 0 Notes on Transition to Display Off Mode
When DES = 0 and DEN = 0, UGM refreshing is not performed if the DSY set value in display
size register Y is less than VDE - VDS. Therefore, if it is wished to set DRES = 0 and DEN = 0,
before the start of the next internal update set a value of VDE - VDS or greater in DSY, and then
set DRES = 0 and DEN = 1. The procedure is shown below.
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