UPD17P136ACT datasheet(123/292 Pages) NEC

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CHAPTER 12 PORTS

104

12.4 PORT 0D (P0D0/SCK, P0D1/SO, P0D2/SI, P0D3/TM0OUT)

Port 0D is a 4-bit input/output port with an output latch. It is mapped into address 73H of BANK0 in data memory.

The output format is N-ch open-drain output. The mask option can be used to specify that a pin contain a pull-up

resistor in 1-bit unit.

Input or output can be specified in 1-bit unit. Input/output is specified with P0DBIO0 to P0DBIO3 (address 2BH)

in the register file.

If P0DBIOn is 0 (n = 0 to 3), the P0Dn pins are used as input port. Pin statuses are read if a data read instruction

is executed for the port register. If P0DBIOn is 1, the P0Dn pins are used as output port and the value written in the

output latch are output to pins. If a data read instruction is executed when pins are used as output ports, the output

latch value, rather than pin statuses, is fetched.

At reset, P0DBIOn is set to 0 and all P0D pins become input ports. The contents of the port output latch become

0. The output latch contents remain unchanged even if P0DBIOn changes from 1 to 0.

Port 0D can also be used for serial interface input/output or timer 0 output. SIOEN (0BH bit 0) in the register file

is used to switch ports (P0D0 to P0D2) to serial interface input/output (SCK, SO, SI) and vice versa. TM0OSEL (bit

3 at address 0BH) in the register file is used to switch a port (P0D3) to timer 0 output (TM0OUT) and vice versa. If

TM0OSEL = 1 is selected, 1 is output at timer 0 reset. This output is inverted every time a timer 0 count value matches

the modulo register contents.

Table 12-4. Register File Contents and Pin Functions

P0D0/SCK

P0D1/SO

P0D2/SI

P0D3/TM0OUT

Input port

Output port

Input port

Output port

Input port

Output port

TM0OUT

SCK

Pin function

TM0OSEL

RF: 0BH

Bit 3

SIOEN

RF: 0BH

Bit 0

P0DBIOn

RF: 2BH

Bit n

(n = 0 to 3)

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