9.12 Port B
9.12.1 Overview
Port B is an 8-bit input/output port that is also used for output (TP
15
to TP
8
) from the
programmable timing pattern controller (TPC), input/output (TIOCB
4
, TIOCB
3
, TIOCA
4
,
TIOCA
3
) and output (TOCXB
4
, TOCXA
4
) by the 16-bit integrated timer unit (ITU), input
(
DREQ
1
,
DREQ
0
) to the DMA controller (DMAC),
ADTRG
input to the A/D converter, and
CS
7
output. A reset or hardware standby leaves port B as an input port. Usage of pins for TPC, ITU,
DMAC, and A/D converter input and output is described in the sections on those modules. For
output of
CS
7
in modes 1 to 6, see section 6.3.2, Chip Select Signals. Pins not assigned to any of
these functions are available for generic input/output. Figure 9-11 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
darlington transistor pair. Pins PB
3
to PB
0
have Schmitt-trigger inputs.
284
www.DataSheet4U.com