Port 12; Block Diagram Of P120 To P127 - NEC mPD780208 Subseries User Manual

4.2.10 Port 12

Port 12 is an 8-bit I/O port with an output latch. The P120 to P127 pins can be set to input mode/output mode
in 1-bit units using port mode register 12 (PM12). In mask ROM versions, use of pull-down resistors can be specified
in 1-bit units with the mask option. Pull-down resistor connection to V
The µ PD78P0208 does not contain pull-down resistors.
Port 12 can drive LEDs directly.
Alternate functions include VFD controller/driver display output.
RESET input sets port 12 to input mode.
Figure 4-13 shows a block diagram of port 12.
Caution Adjust the number of pull-down resistors so that the total power dissipation (refer to 15.10
Calculating Total Power Dissipation) is not exceeded.
RD
WR
PORT
WR
PM
Alternate function
PM: Port mode register
RD: Port 12 read signal
WR: Port 12 write signal
94
CHAPTER 4 PORT FUNCTIONS
Figure 4-13. Block Diagram of P120 to P127
Selector
Output latch
(P120 to P127)
PM120 to PM127
User's Manual U11302EJ4V0UM
or V can be specified in 4-bit units.
LOAD SS
Mask option
Only mask ROM
versions.
µ
The PD78P0208
has no pull-down
resistors.
P120/FIP45
to
P127/FIP52
V
LOAD