NEC PD750008 - Manual (Page 68)

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µPD750008 USER'S MANUAL
4.3 PROGRAM MEMORY (ROM):
4096 WORDS x 8 BITS (µPD750004: MASKED ROM)
6144 WORDS x 8 BITS (µPD750006: MASKED ROM)
8192 WORDS x 8 BITS (µPD750008: MASKED ROM)
16384 WORDS x 8 BITS (µPD75P0016: ONE-TIME PROM)
The program memory is used for storing programs, an interrupt vector table, GETI instruction reference
table, table data, and so forth. The µPD750004, µPD750006, and µPD750008 are provided with a mask-
programmable ROM as the program memory, and the µPD75P0016 is provided with a one-time PROM.
Figures 4-3 to 4-6 show the program memory maps.
Program memory is addressed by the program counter. Table data can be referenced using the table
reference instruction (MOVT).
Figures 4-3 to 4-6 also show the allowable branch address ranges for the branch instructions and subroutine
call instructions. The relative branch instruction (BR $addr) allows a branch to addresses (contents of the
PC less 15 to one, or plus two to 16) regardless of block.
The program memory is located at following addresses.
• 0000H to 0FFFH: µPD750004
• 0000H to 17FFH: µPD750006
• 0000H to 1FFFH: µPD750008
• 0000H to 3FFFH: µPD75P0016
The following addresses are assigned to special functions. All areas excluding 0000H and 0001H can be
used as normal program memory.
• 0000H to 0001H
Vector address table for holding the RBE and MBE values and program start address when a RESET
signal is issued (allowing a reset start at an arbitrary address)
• 0002H to 000DH
Vector address table for holding the RBE and MBE values and program start address for each vectored
interrupt (allowing interrupt processing to be started at an arbitrary address)
• 0020H to 007FH
Table area referenced by the GETI instruction Note
Note The GETI instruction can represent an arbitrary two-byte or three-byte instruction or two one-byte
instructions in one byte and is used to reduce the number of program bytes. (See Section 11.1.1.)