![NEC mPD17120 Subseries User Manual Download Page 84](http://html.mh-extra.com/html/nec/mpd17120-subseries/mpd17120-subseries_user-manual_249259084.webp)
CHAPTER 8 GENERAL REGISTER (GR)
The general register (GR) is allocated in data memory. It can therefore be used directly in performing arithmetic/
logical operations with and in transferring data to and from general data memory.
8.1 GENERAL REGISTER CONFIGURATION
Figure 8-1 shows the configuration of the general register.
As shown in Figure 8-1, sixteen nibbles in a single row address in data memory (16
×
4 bits) are used as the general
register.
The general register pointer (RP) in the system register is used to indicate which row address is to be used as
the general register. Because the RP effectively has three valid bits, the data memory row addresses in which the
general register can be allocated are address locations 0H to 7H. However, note that addresses 40H to 6EH are
uninstalled memory locations and should therefore not be specified as locations for the general register.
8.2 FUNCTIONS OF THE GENERAL REGISTER
The general register can be used in transferring data to and from data memory within an instruction. It can also
be used in performing arithmetic/logical operations with data memory within an instruction. In effect, since the
general register is data memory, this just means that operations such as arithmetic/logical operations and data transfer
can be performed on and between locations in data memory. In addition, because the general register is allocated
in data memory, it can be controlled in the same manner as other areas in data memory through the use of data
memory manipulation instructions.
69
Summary of Contents for mPD17120 Subseries
Page 15: ... x MEMO ...
Page 23: ... MEMO 8 ...
Page 45: ... MEMO 30 ...
Page 49: ... MEMO 34 ...
Page 55: ... MEMO 40 ...
Page 93: ... MEMO 78 ...
Page 99: ... MEMO 84 ...
Page 102: ...CHAPTER 11 ARITHMETIC AND LOGIC UNIT 87 MEMO ...
Page 119: ... MEMO 104 ...
Page 175: ... MEMO 160 ...
Page 199: ... MEMO 184 ...
Page 265: ... MEMO 250 ...
Page 281: ...266 MEMO ...
Page 285: ... MEMO 270 ...
Page 289: ... MEMO 274 ...