w78e516b Winbond Electronics Corp America, w78e516b Datasheet - Page 9

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

5.9 Port 4
Port 4, address D8H, is a 4-bit multipurpose programmable I/O port. Each bit can be configured
individually by software. The Port 4 has four different operation modes.
Mode 0: P4.0 − P4.3 is a bi-directional I/O port which is same as port 1. P4.2 and P4.3 also serve as
Mode 1: P4.0 − P4.3 are read strobe signals that are synchronized with RD signal at specified
Mode 2: P4.0 − P4.3 are write strobe signals that are synchronized with WR signal at specified
Mode 3: P4.0 − P4.3 are read/write strobe signals that are synchronized with RD or WR signal at
When Port 4 is configured with the feature of chip-select signals, the chip-select signal address range
depends on the contents of the SFR P4xAH, P4xAL, P4CONA and P4CONB. The registers P4xAH
and P4xAL contain the 16-bit base address of P4.x. The registers P4CONA and P4CONB contain the
control bits to configure the Port 4 operation mode.
5.10
Two additional external interrupts, INT2 and INT3 , whose functions are similar to those of external
interrupt 0 and 1 in the standard 80C52. The functions/status of these interrupts are
determined/shown by the bits in the XICON (External Interrupt Control) register. The XICON register is
bit-addressable but is not a standard register in the standard 80C52. Its address is at 0C0H. To
set/clear bits in the XICON register, one can use the "SETB ( CLR ) bit" instruction. For example,
"SETB 0C2H" sets the EX2 bit of XICON.
INT2
external interrupt INT3 and INT2 if enabled.
addresses. These signals can be used as chip-select signals for external peripherals.
addresses. These signals can be used as chip-select signals for external peripherals.
specified addresses. These signals can be used as chip-select signals for external
peripherals.
/
INT3
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Publication Release Date: April 22, 2008
W78E516B
Revision A12