NEC PD17062 Manuale Utente

µ

The general-purpose register pointer points to the bank and row address of the general-purpose register.

However, since RPH of the 

µ

PD17062 is fixed at 0, only RPL (3 bits) can be specified.  This means that 0

to 7 can be specified as a register pointer.  Hence, in the 

µ

PD17062, the row address of the general-purpose

register can be specified anywhere within BANK0.

The program status word consists of a flag that indicates the result of operation by the ALU in the CPU and

a 5-bit flag that modifies the ALU function.  PSWORD has a binary coded decimal (BCD) flag, compare (CMP)

flag, carry (CY) flag, zero (Z) flag, and index enable (IXE) flag.  Fig. 8-6 shows the functions of these flags.

b

0

b

3

b

2

b

1

b

0

BCD

CMP

CY

Z

IXE

When the arithmetic operation result is other than 0, this flag 
is reset.  The set condition differs according to the contents of 
the CMP flag. 

7EH

7FH

Index
enable
flag

When this flag is set, index modification is enabled.

Zero flag

(1)  When CMP = 0
      The flag is set when the arithmetic operation result is 0.
(2)  When CMP = 1
      The flag is set when the result of the arithmetic operation
      executed at Z = 1 is 0.

Carry flag

The carry flag is set when a carry occurs during the execution 
of an addition instruction or when a borrow occurs during the 
execution of a subtraction instruction.  This flag is reset when 
neither carry nor borrow occurs.
This flag is set when the least significant bit of the general-
purpose register is 1, in which the RORC instruction is executed.  
The flag is reset when the bit is 0.

Compare
flag

When this flag is set, the arithmetic operation result is not 
stored into data memory.
The CMP flag is reset automatically when the SKT or SKF 
instruction is executed.

BCD flag

When this flag is set, all arithmetic operations are executed in 
decimal.  When this flag is not set, all arithmetic operations are 
executed in binary.