HD404328 Datasheet, PDF (12/96 Pages) Hitachi Semiconductor – 4 BIT SINGLE CHIP MICROCOMPUTER

HD404328 Series
Interrupt Control Bits Area and Register Flag Area ($000–$003, $020–$023): Used for interrupt
control bits and the bit register (figure 3). This area can be accessed only by RAM bit manipulation
instructions. In addition, note that the interrupt request flag cannot be set by software, the RSP bit is used
only to reset the stack ppointer, and the WDON flag can be set only by the SEM and SEMD instructions.
Special Function Registers Area ($004–$01F, $024–$03F): Used as mode registers for external
interrupts, serial interface, and timer/counters, and as data registers and as data control registers for I/O
ports. As shown in figure 2, these registers can be classified into three types: write-only, read-only, and
read/write. The SEM, SEMD, REM, and REMD instructions can be used for the LCD control register
(LCR), but RAM bit manipulation instructions cannot be used for other registers.
LCD Data Area ($050–$067): Used for storing LCD data which is automatically output to LCD segments
as display data. Data 1 lights the corresponding LCD segment; data 0 extinguishes it.
Data Area (HD404324, HD404324U, HD404326, HD404326U, HD404328, HD404328U: $040–$04F
and $070–$11F, HD4074329, HD4074329U: $040–$04F and $070–$21F): The memory registers (MR),
which consist of 16 digits ($040–$04F), can be accessed by the LAMR and XMRA instructions. Its
structure is shown in figure 4.
Stack Area ($3C0–$3FF): Used for saving the contents of the program counter (PC), status flag (ST), and
carry flag (CA) at subroutine calls (CAL, CALL) and interrupts. This area can be used as a 16-level
nesting subroutine stack in which one level requires four digits. The data to be saved and the save
conditions are shown in figure 4.
The program counter is restored by either the RTN or RTNI instruction, but the status and carry flags can
only be restored by the RTNI instruction. Any unused space in this area is used for data storage.
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