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9.12 Port B
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9.12.1 Overview
Port B is an 8-bit input/output port that is also used for output (TP
programmable timing pattern controller (TPC), input/output (TIOCB
TIOCA
) and output (TOCXB
3
, DREQ
) to the DMA controller (DMAC), ADTRG input to the A/D converter, and CS
(DREQ
1
0
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
in modes 1 to 6, see section 6.3.2, Chip Select Signals. Pins not assigned to any of
7
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
, TOCXA
) by the 16-bit integrated timer unit (ITU), input
4
4
to PB
have Schmitt-trigger inputs.
3
0
284
to TP
) from the
15
8
, TIOCB
, TIOCA
,
4
3
4
7
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