Epson S2R72V18 Technical Manual page 183

1. Functions
For cases in which writing occurs only to Low from a state in which byte boundaries do not
exist in the FIFO, this writing will be ignored (Fig. 1-78 (5)). If word writing from a state in
which byte boundaries do not exist in the FIFO and the quantity that can be written is "1,"
writing to Low will be ignored and only writing to High will be performed (Fig. 1-78 (6)). In
other words, the operation is identical to that performed when writing to High.
Before writing
OP
start
Writing Q to
High and R
to Low
Before writing
start
Writing R to
Low
[Reading]
If there are no byte boundaries, there should be no problem with word-reading using the
FIFO_Rd_0,1 registers or byte-reading using the FIFO_ByteRd register. If there are byte
boundaries, read using the FIFO_ByteRd register. There should be no problem with
word-reading or byte-reading after the byte boundaries have been temporarily cleared.
Fig. 1-79 (1) shows the situation when word-reading from a state without byte boundaries.
Data A and B followed by data C and D are read out for each access. Fig. 1-79 (2) shows the
situation when byte-reading. For each access, data is read out in the sequence A, B, C, and D.
These are the normal read operations.
Before reading
OA OB
OC OD
start
166
After writing
OP OR
start
Writing R and
ignoring Q
(3)
After writing
start
Ignoring R
(5)
Fig. 1-78 FIFO writing processing (caution required)
After reading
OC
start
(1)
Fig. 1-79 FIFO reading processing (normal operation)
Before writing
OP
start
Writing Q to
Before writing
(quantity for writing 1 )
OB
start
Writing S to
High and T
Before reading
OD
start
EPSON
start
High
(4)
" "
OA
OC
start
to Low
(6)
OA OB
OC OD
start
(2)
S2R72V18 Technical Manual (Rev.1.00)
After writing
OP
Ignoring Q
After writing
OS OA
OB OC
Writing S and
ignoring T
After reading
OB
OC OD