参数资料
型号: M34518E8SP
元件分类: 微控制器/微处理器
英文描述: 4-BIT, OTPROM, 6 MHz, MICROCONTROLLER, PDIP32
封装: 8.90 X 28 MM, 1.78 MM PITCH, PLASTIC, SDIP-32
文件页数: 76/162页
文件大小: 1149K
代理商: M34518E8SP
Rev.3.01
2005.06.15
page 18 of 157
REJ03B0008-0301
4518 Group
(8) Program counter (PC)
Program counter (PC) is used to specify a ROM address (page and
address). It determines a sequence in which instructions stored in
ROM are read. It is a binary counter that increments the number of
instruction bytes each time an instruction is executed. However,
the value changes to a specified address when branch instructions,
subroutine call instructions, return instructions, or the table refer-
ence instruction (TABP p) is executed.
Program counter consists of PCH (most significant bit to bit 7)
which specifies to a ROM page and PCL (bits 6 to 0) which speci-
fies an address within a page. After it reaches the last address
(address 127) of a page, it specifies address 0 of the next page
(Figure 7).
Make sure that the PCH does not specify after the last page of the
built-in ROM.
(9) Data pointer (DP)
Data pointer (DP) is used to specify a RAM address and consists
of registers Z, X, and Y. Register Z specifies a RAM file group, reg-
ister X specifies a file, and register Y specifies a RAM digit (Figure
8).
Register Y is also used to specify the port D bit position.
When using port D, set the port D bit position to register Y certainly
and execute the SD, RD, or SZD instruction (Figure 9).
Note
Register Z of data pointer is undefined after system is released
from reset.
Also, registers Z, X and Y are undefined in the RAM back-up. After
system is returned from the RAM back-up, set these registers.
Fig. 7 Program counter (PC) structure
Fig. 8 Data pointer (DP) structure
Fig. 9 SD instruction execution example
p5 p4 p3 p2 p1 p0
a6 a5 a4 a3 a2 a1 a0
Program counter
PCH
Specifying page
PCL
Specifying address
p6
Z1 Z0 X3 X2 X1 X0 Y3 Y2 Y1 Y0
Data pointer (DP)
Register Z (2)
Register X (4)
Register Y (4)
Specifying
RAM digit
Specifying RAM file
Specifying RAM file group
0
01
1
Set
Specifying bit position
Port D output latch
Register Y (4)
D2
D3
D1
D0
0
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