W78E516DDG Datasheet, PDF (34/90 Pages) Nuvotem Talema – 8-BIT MICROCONTROLLER

W78E516D/W78E058D Data Sheet
7 CY
Carry flag:
Set for an arithmetic operation which results in a carry being generated from the
ALU. It is also used as the accumulator for the bit operations.
6 AC
Auxiliary carry:
Set when the previous operation resulted in a carry from the high order nibble.
5 F0
User flag 0:
The General purpose flag that can be set or cleared by the user.
4 RS1 Register bank select bits:
3 RS0 Register bank select bits:
2 OV
Overflow flag:
Set when a carry was generated from the seventh bit but not from the 8^th bit as a
result of the previous operation, or vice-versa.
1 F1
User Flag 1:
The General purpose flag that can be set or cleared by the user by software.
0P
Parity flag:
Set/cleared by hardware to indicate odd/even number of 1’s in the accumulator.
RS.1-0: Register bank selection bits:
RS1 RS0 Register bank Address
0
0
0
00-07h
0
1
1
08-0Fh
1
0
2
10-17h
1
1
3
18-1Fh
Port 4
Bit: 7
6
5
4
3
2
1
0
-
-
-
-
P4.3
P4.2
P4.1
P4.0
Mnemonic: P4
Address: D8h
Port 4, SFR P4 at address D8H, is a 4-bit multipurpose programmable I/O port. Each bit can be con-
figured individually by software. The Port 4 has four different operation mode:
In 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
external interrupt INT3 and INT2 if enabled.
In mode 1, P4.0−P4.3 are read data strobe signals which are synchronized with RD signal at specified
addresses. These signals can be used as chip-select signals for external peripherals.
In mode 2 , P4.0−P4.3 are write data strobe signals which are synchronized with WR signal at speci-
fied addresses. These signals can be used as chip-select signals for external peripherals.
In mode 3, P4.0−P4.3 are read data strobe signals which are synchronized with RD or WR signal at
specified addresses. These signals can be used as chip-select signals for external peripherals.
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.
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