Bank Register (Pcb, Dtb, Usb, Ssb, And Adb) - Fujitsu MB90420/5 (A) Series Hardware Manual

2.7.9 Bank Register (PCB, DTB, USB, SSB, and ADB)

The bank register specifies the most significant 8-bit address using bank type addressing and consists of the
following five registers:
• Program bank register (PCB)
• Data bank register (DTB)
• User stack bank register (USB)
• System stack bank register (SSB)
• Additional bank register (ADB)
Each of the above registers indicates the memory bank to which the program space, data space, user stack
space, system stack space, or additional space is allocated.
n Bank register (PCB, DTB, USB, SSB, and ADB)
• Program bank register (PCB)
The PCB specifies the program (PC) space. It is rewritten at execution of the JMPP, CALLP, RETP, or
RETI instruction that branches to the entire 16-Mbyte space, at executing a software interrupt instruction,
or at a hardware interrupt or exception.
• Data bank register (DTB)
The DTB specifies the data (DT) space.
• User stack bank register (USB) and system stack bank register (SSB)
The USB and SSB indicate the stack (SP) space. Whether the USB or the SSB is used depends on the
value of the S flag in the processor status (PS: CCR). For details, see Section 2.7.2.
• Additional bank register (ADB)
The ADB specifies the additional (AD) space.
• Setting of each bank and data access
All bank registers are byte-length. By a reset, the PCB is initialized to FF
initialized to 00 . The PCB can be read but cannot be written. Bank registers other than the PCB can be
H
both read and written.
Note: The MB90420/5 (A) series supports up to the memory space contained in the device.
For the operation of each register, see Section 2.4.2.
CPU
2-27
and the other bank registers are
H