參數(shù)資料
型號(hào): μPD789405
廠商: NEC Corp.
英文描述: 8 Bit Single Chip Microcontrollers(8位單片微控制器)
中文描述: 8位單片機(jī)微控制器(8位單片微控制器)
文件頁數(shù): 88/128頁
文件大?。?/td> 607K
代理商: ΜPD789405
88
μ
PD789405, 789406, 789407
(5) Program status word (PSW)
The program status word is used to hold the instruction execution result and the current status of the interrupt
requests. The IE flag, used to enable and disable maskable interrupts, is mapped to the PSW.
The PSW can be read- and write-accessed in 8-bit units, as well as in 1-bit units when using bit manipulation
instructions and dedicated instructions (EI and DI). When a vector interrupt is accepted, the PSW is
automatically saved to a stack, and the IE flag is reset (0).
An RESET input loads 02H into the PSW.
Figure 6-6. Program Status Word Configuration
IE
Z
0
AC
0
0
1
CY
PSW
Symbol
When reset
02H
7
6
5
4
3
2
1
0
IE
0
1
Disable
Enable
Whether to enable/disable interrupt acceptance
Used in the execution of ordinary instructions
(6) Key return mode register (KRM)
The KRM is used to specify the pin at which a key return signal is detected.
The KRM is set using a 1-bit or 8-bit memory manipulation instruction.
Bit 0 (KRM0) is set in 4-bit units for the KR0/P40 to KR3/P43 pins. Bits 4 and 5 (KRM4 and KRM5) are set in
1-bit units for the KR4/P44 and KR5/P45 pins, respectively.
A RESET input clears the KRM to 00H.
Figure 6-7. Key Return Mode Register Format
KRMn
0
1
Key return signal detection selection
Undetected
Detected (at the falling edge of port 4)
0
0
KRM5KRM4
0
0
0
KRM0
KRM
Symbol
Address
When reset
R/W
FFF5H
00H
R/W
7
6
5
4
3
2
1
0
Cautions 1. Bits 1, 2, 3, 6, and 7 must be fixed to 0.
2.
When KRM is set (1), the corresponding output pin is connected to a pull-up resistor
unless it is in output mode. In output mode, the pull-up resistor is not connected.
3.
Before setting the KRM, set bit 5 of MK1 (KRMK = 1) to disable interrupts.
To enable interrupts, clear bit 5 of IF1 (KRIF = 0), then bit 5 of MK1 (KRMK = 0).
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