UPD784915B Datasheet, PDF (20/86 Pages) NEC – 16-BIT SINGLE-CHIP MICROCONTROLLERS

µPD784915B, 784916B
3.1.2 Other CPU registers
(1) Program counter
The program counter of the µPD784916B is 20 bits wide. The value of the program counter is automatically
updated as the program is executed.
19
0
PC
(2) Program status word
This is a register that holds the various statuses of the CPU. Its contents are automatically updated as the program
is executed.
15 14 13 12 11 10 9 8
PSWH UF RBS2 RBS1 RBS0
PSW
7
PSWL S
6543210
Z
Note
RSS
AC
IE
P/V
0
CY
Note The RSS flag is provided to maintain compatibility with the microcontrollers in the 78K/III Series. Always
set this flag to 0 except when the software of the 78K/III Series is used.
(3) Stack pointer
This is a 24-bit pointer that holds the first address of the stack.
Be sure to write 0 to the high-order 4 bits.
23
20
0
SP 0 0 0 0
3.2 Memory Space
The µPD784916B can access a 64 Kbyte memory space.
Table 3-1 shows the addresses of the internal ROM and internal data areas.
Table 3-1. Memory Space
Part Number
µPD784915B
µPD784916B
Internal ROM Area
0000H-BFFFH
0000H-F7FFH
Internal Data Area
FA00H-FFFFH
Caution
Some products in the 78K/IV Series can access up to 1 Mbyte of memory space in an address
expansion mode which is set by the LOCATION instruction. However, the memory space of the
µPD784916B is 64 Kbytes (0000H to FFFFH). Therefore, be sure to execute the LOCATION 0
instruction immediately after reset to set the memory space to 64 Kbytes (the LOCATION
instruction cannot be used more than twice).
20