BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
400
Section 13: GPIO
Document
1250_1125-UM100CB-R
O
THER
P
INS
T
HAT
C
AN
B
E
U
SED
The part has many built in peripherals, and in any particular application it is possible that some of them are not
used. Pins on some of the peripherals can be used to provide additional software controlled input, output or
interrupt lines. This section describes some of these.
S
ERIAL
P
ORTS
If a serial port is unused most of its pins can be reused. The port should be configured in asynchronous mode.
All of the input pins (except for the data input pin) can be read through the
duart_in_port
register. The output
handshake pins can be used by configuring them for software control. In an extreme case it would be possible
to use the data out pin by enabling the transmitter and either letting the line idle (by sending nothing) to give a
high output, or sending a break to give a low output.
The following table summarizes the pins that can be directly used.
See
Section: “Operation” on page 323
for how to configure the UART and control the I/O lines.
PCI
If the PCI bus is not used the PCI interrupt lines can be used as active low level interrupt inputs, as can the
SERR and PERR signals. If the PCI is in device mode the P_INTB_L, P_INTC_L and P_INTD_L lines can be
used as active low level interrupt lines.
MAC
S
The MAC management interface provides the only pins that can easily be used from an unused MAC interface.
The MDIO line provides input and output, and the MDC line is output only. The GENO pin from a MAC is
available as a general output unless the interface is in 16 bit bypass mode. The FIFO mode of the MAC may
be used for bulk data DMA transfers, but there is no easy way to use it for programmed I/O.
PCMCIA P
OWER
C
ONTROL
P
INS
The PCMCIA power control pins are three dedicated outputs that are forced low when the part is reset. If
PCMCIA support is not required then these lines can be used as general outputs by setting the PCMCIA power
logic for software power control and writing the power control bits. This is described in
Table 284: Other Pins that can be Used as General Inputs or Outputs
Pin Name
Direction
Channel A access
(n=0)
Channel B access
(n=1)
Sn_RTS_TSTROBE
Output
op[0]
op[1]
Sn_COUT
Output
op[2]
op[3]
Sn_CTS_TCLKIN
Input transition detect
ip[0]
ip[1]
Sn_CIN_RCLKIN
Input transition detect
ip[2]
ip[3]
Sn_TIN
Input
ip[4]
ip[5]
Sn_RIN
Input
ip[6]
ip[7]