w78e516b Winbond Electronics Corp America, w78e516b Datasheet - Page 13

• Manufacturer Part Number: w78e516b
• Description: 8-bit Microcontroller
• Manufacturer: Winbond Electronics Corp America

P4 (D8H)
Here is an example to program the P4.0 as a write strobe signal at the I/O port address 1234H −
1237H and positive polarity, and P4.1 − P4.3 are used as general I/O ports.
MOV P40AH, #12H
MOV P40AL, #34H
MOV P4CONA, #00001010B
MOV P4CONB, #00H
MOV P2ECON, #10H
Then any instruction MOVX @DPTR, A (with DPTR = 1234H − 1237H) will generate the positive
polarity write strobe signal at pin P4.0. And the instruction MOV P4, #XX will output the bit3 to bit1 of
data #XX to pin P4.3 − P4.1.
BIT
7
6
5
4
3
2
1
0
NAME
P43
P42
P41
P40
-
-
-
-
Reserve
Reserve
Reserve
Reserve
Port 4 Data bit which outputs to pin P4.3 at mode 0.
Port 4 Data bit which outputs to pin P4.2 at mode 0.
Port 4 Data bit which outputs to pin P4.1at mode 0.
Port 4 Data bit which outputs to pin P4.0 at mode 0.
; Base I/O address 1234H for P4.0
; P4.1 − P4.3 as general I/O port which are the same as PORT1
; Write the P40SINV = 1 to inverse the P4.0 write strobe polarity
; default is negative.
; P4.0 a write strobe signal and address line A0 and A1 are masked.
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FUNCTION
Publication Release Date: April 22, 2008
W78E516B
Revision A12