NEC PD78F9488 - Manual (Page 80)

CHAPTER 4 PORT FUNCTIONS
80
User’s Manual U15331EJ4V1UD
Figure 4-5. Block Diagram of P21
Internal bus
V DD
P21/SO20/TxD20
WR PUB2
RD
WR PORT
WR
PM
PUB21
Alternate
function
Output latch
(P21)
PM21
Selector
P-ch
PUB2: Pull-up resistor option register B2
PM:
Port mode register
RD: Port 2 read signal
WR: Port 2 write signal