Port 3 - NEC mPD780852 Series Preliminary User's Manual

4.2.4 Port 3

Port 3 is an 8-bit output only port with output latch. P30 to P37 pins go into a high-impedance state when the ENn
of port mode control register (PMC) is set to 0 and the port mode register 3 (PM3) is set to 1.
Alternate functions include meter control PWM output.
RESET input sets port 3 to high-impedance state.
Figure 4-5 shows a block diagram of port 3.
RD
WR
PORT
WR
PM
PM: Port mode register
RD: Port 3 read signal
WR: Port 3 write signal
Caution When PM3 is set to 0, read operation is enabled. When PM3 is set to 1, read operation is disabled.
Remark n = 3, 4
80
CHAPTER 4 PORT FUNCTIONS
Figure 4-5. P30 to P37 Block Diagram
Output latch
(P30 to P37)
PM30 to PM37
Alternate
functions
Preliminary User's Manual U14581EJ3V0UM00
Decoder
2
MODn ENn DIRn1 DIRn0
P30/SM31 to P33/SM34
P34/SM41 to P37/SM44