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7.11 Port B
7.11.1 Overview
Port B is an 7-bit input/output port that is also used for TPC output (TP
15
, TP
13
to TP
8
), ITU
input/output (TIOCB
4
, TIOCB
3
, TIOCA
4
, TIOCA
3
) and ITU output (TOCXB
4
, TOCXA
4
), and
ADTRG
input to the A/D converter. Port B has the same set of pin functions in all operating
modes. Figure 7-23 shows the pin configuration of port B.
Pins in port B can drive one TTL load and a 30-pF capacitive load. They can also drive an LED or
a Darlington transistor pair. Pins PB
3
to PB
0
have Schmitt-trigger inputs.
Port B
PB (input/output)/TP (output)/
ADTRG
(input)
PB (input/output)/TP (output)/TOCXB (output)
PB (input/output)/TP (output)/TOCXA (output)
7
5
4
3
2
1
0
Port B pins
15
13
12
11
10
9
8
4
4
PB (input/output)/TP (output)/TIOCB (input/output)
PB (input/output)/TP (output)/TIOCA (input/output)
PB (input/output)/TP (output)/TIOCB (input/output)
PB (input/output)/TP (output)/TIOCA (input/output)
4
4
3
3
Figure 7-23 Port B Pin Configuration
7.11.2 Register Descriptions
Table 7-17 summarizes the registers of port B.
Table 7-17 Port B Registers
Address
*
Name
Abbreviation
R/W
Initial Value
H'FFD4
Port B data direction register
PBDDR
W
H'00
H'FFD6
Port B data register
PBDR
R/W
H'00
Note:
*
Lower 16 bits of the address.