HD404356 Datasheet, PDF (7/100 Pages) Hitachi Semiconductor – 4-bit HMCS400-Series microcomputer

HD404358 Series
RAM Memory Map
The HD404354, HD40A4354, HD404356, HD40A4356, HD404358 and HD40A4358 MCUs contain 384-
digit × 4-bit RAM areas. The HD407A4359 MCU contain 512-digit × 4-bit RAM areas. Both of these
RAM areas consist of a memory register area, a data area, and a stack area. In addition, an interrupt control
bits area, special function register area, and register flag area are mapped onto the same RAM memory
space labeled as a RAM-mapped register area. The RAM memory map is shown in figure 2 and described
below.
RAM-Mapped Register Area ($000–$03F):
• Interrupt Control Bits Area ($000–$003)
This area is used for interrupt control bits (figure 3). These bits can be accessed only by RAM bit
manipulation instructions (SEM/ SEMD, REM/REMD, and TM/TMD). However, note that not all the
instructions can be used for each bit. Limitations on using the instructions are shown in figure 4.
• Special Function Register Area ($004–$01F, $024–$03F)
This area is used as mode registers and data registers for external interrupts, serial interface,
timer/counters, A/D converter, and as data control registers for I/O ports. The structure is shown in
figures 2 and 5. These registers can be classified into three types: write-only (W), read-only (R), and
read/write (R/W). RAM bit manipulation instructions cannot be used for these registers.
• Register Flag Area ($020–$023)
This area is used for the DTON, WDON, and other register flags and interrupt control bits (figure 3).
These bits can be accessed only by RAM bit manipulation instructions (SEM/ SEMD, REM/REMD,
and TM/TMD). However, note that not all the instructions can be used for each bit. Limitations on
using the instructions are shown in figure 4.
Memory Register (MR) Area ($040–$04F): Consisting of 16 addresses, this area (MR0–MR15) can be
accessed by register-register instructions (LAMR and XMRA). The structure is shown in figure 6.
Data Area ($050–$17F for HD404354/HD40A4354/HD404356/HD40A4356/HD404358/HD40A4358,
$050–$1FF for HD407A4359)
Stack Area ($3C0–$3FF): Used for saving the contents of the program counter (PC), status flag (ST), and
carry flag (CA) at subroutine call (CAL or CALL instruction) and for 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 6.
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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