NEC uPD78P078 - Manual (Page 156)

156
CHAPTER 6 PORT FUNCTIONS
6.2.14 Port 13
This is a 2-bit input/output port with output latches. Input mode/output mode can be specified in 1-bit units with
the port mode register 13 (PM13). When pins P130 and P131 are used as input port pins, an on-chip pull-up resistor
can be connected in 2-bit units with a pull-up resistor option register H (PUOH).
These pins are dual function pin and serve as D/A converter analog outputs.
RESET input sets the input mode.
The port 13 block diagram is shown in Figure 6-23.
Caution When only either one of the D/A converter channels is used with AV REF1 < V DD , the other
pins that are not used as analog outputs must be set as follows:
• Set PM13x bit of the port mode register 13 (PM13) to 1 (input mode) and connect the pin
to V
SS
.
• Set PM13x bit of the port mode register 13 (PM13) to 0 (output mode) and the output latch
to 0, to output low level from the pin.
Figure 6-23. Block Diagram of P130 and P131
PUO : Pull-up resistor option register
PM : Port mode register
RD : Port 13 read signal
WR : Port 13 write signal
P-ch
WR
PM
WR PORT
RD
WR
PUO
V DD
Selector
PUO13
Output Latch
(P130, P131)
PM130, PM131
Internal bus
P130/ANO0,
P131/ANO1