Specifications

EPSON 9–9
SED1278
SED1278
Read Only Instructions
Read Busy Flag/Address Counter
DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
BF ACC
RS = 1
Reading the instruction register yields the current value
of the address counter and the busy flag. This instruction
must be executed prior to any other instructions.
•A
CC, the address counter value, will point to a location
in either CGRAM or DDRAM, depending on the type
of “Set RAM Address” instruction last sent.
In “Busy Flag Check” immediately after executing
“RAM Address Set” instruction, a valid address counter
value can be read 5 clock cycles after the busy flag
(BF) goes low.
In “Busy Flag Check” immediately after executing
“Write Data” instruction, a valid address counter
value can be ready as soon as BF goes low.
• The BF bit shows the status of the busy flag.
• BF = 1: SED1278 busy.
• BF = 0: SED1278 ready for next instruction.
Read Data
DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
DATA
RS = 1
This instruction reads data from either CGRAM or
DDRAM, depending on the type of “Set RAM Address”
instructions last sent. The address in that space depends
on the “Set RAM Address” instructions parameters.
Immediately before executing “Read Data”, “Set
CGRAM Address” or “Set DDRAM Address” must be
executed.
The contents of the address counter are modified after
each “Read Data”, as determined by “Entry Mode Set”.
Display shift is not executed, independently of “Entry
Mode Set”.