Data Sheet

FLC-BTM901 Datasheet
Flaircomm Microelectronics,Inc. - 33-
12 Peripheral Interfaces
12.1 PIO
BTM901 has the following digital I/O pads:
■ 15 PIO pads
■ 5 x pads intended for LED operation: AIO[5:4, 2:0]
■ 1 x Reset (active low) pad: RES#
■ 1 x Power-on signaling: SYS_CTRL, usable as an input after boot.
■ USB device I/O: If not used for USB purposes, this port is usable as digital I/O
12.2 Standard I/O
The standard digital I/O pins (PIO) on BTM901 are split into separate pad domains. Each
VDD_PADS domain can be separately powered, from 1.7 V to 3.6 V. The VDD_PADS of
a particular pin should be powered before voltages are supplied to PIO powered by that
domain otherwise back powering can occur through the ESD protection in the pad.
PIO can be programmed to have a pull-up or pull down with two strengths (weak and
strong). PIO can also be programmed with a sticky function where they are strongly
pulled to their current input state. PIO have a reset pull state, after reset the pulls can be
re-configured by software.
PIO also have a programmable drive strength capability of 2, 4, 8, or 12 mA.
All PIO are readable by all subsystems, but for write access are assigned by software to
particular subsystem control. PIO inputs are via Schmitt triggers.
12.3 Pad Multiplexing
A BTM901 pad’s function is chosen at runtime from multiple potential functions, using
multiplexing.
In the input direction, signals driven into the chip, all PIOs are distributed to each
subsystem and visible on the PIO status bus. It is the subsystem's responsibility to select
I/Os of interest for a particular application.
In the output direction, the System Manager has overall control of PIO allocation and
control. When a PIO is allocated to a particular subsystem, the output is propagated
combinationally from the subsystem to the pad. That is, there are no registers between
the subsystem and the pad.
The LED pins and some other peripheral I/O states can be read as virtual PIO,see Table