PSD834F2-15J STMicroelectronics, PSD834F2-15J Datasheet - Page 47

• Manufacturer Part Number: PSD834F2-15J
• Manufacturer: STMicroelectronics

Specifications of PSD834F2-15J

• Operating Temperature (max): 70C
• Operating Temperature (min): 0C
• Operating Temperature Classification: Commercial
• Package Type: PLCC
• Mounting: Surface Mount
• Pin Count: 52
• Lead Free Status / RoHS Status: Compliant

The Port pin’s tri-state output driver enable is con-
trolled by a two input OR gate whose inputs come
from the CPLD AND Array enable product term
and the Direction Register. If the enable product
term of any of the Array outputs are not defined
and that port pin is not defined as a CPLD output
in the PSDabel file, then the Direction Register has
sole control of the buffer that drives the port pin.
The contents of these registers can be altered by
the MCU. The Port Data Buffer (PDB) feedback
path allows the MCU to check the contents of the
registers.
Ports A, B, and C have embedded Input Macro-
cells (IMC). The Input Macrocells (IMC) can be
configured as latches, registers, or direct inputs to
the PLDs. The latches and registers are clocked
by Address Strobe (ALE/AS, PD0) or a product
term from the PLD AND Array. The outputs from
the Input Macrocells (IMC) drive the PLD input bus
and can be read by the MCU. See the section en-
titled “Input Macrocell”, on page 36.
Port Operating Modes
The I/O Ports have several modes of operation.
Some modes can be defined using PSDabel,
some by the MCU writing to the Control Registers
in CSIOP space, and some by both. The modes
that can only be defined using PSDsoft Express
must be programmed into the device and cannot
be changed unless the device is reprogrammed.
The modes that can be changed by the MCU can
be done so dynamically at run-time. The PLD I/O,
Data Port, Address Input, and Peripheral I/O
modes are the only modes that must be defined
before programming the device. All other modes
can be changed by the MCU at run-time. See Ap-
plication Note AN1171 for more detail.
Table 18 summarizes which modes are available
on each port. Table 21 shows how and where the
different modes are configured. Each of the port
operating modes are described in the following
sections.
MCU I/O Mode
In the MCU I/O mode, the MCU uses the I/O Ports
block to expand its own I/O ports. By setting up the
CSIOP space, the ports on the PSD are mapped
into the MCU address space. The addresses of
the ports are listed in Table 6.
A port pin can be put into MCU I/O mode by writing
a 0 to the corresponding bit in the Control Regis-
ter. The MCU I/O direction may be changed by
writing to the corresponding bit in the Direction
Register, or by the output enable product term.
See the section entitled “Peripheral I/O Mode”, on
page 49. When the pin is configured as an output,
the content of the Data Out Register drives the pin.
When configured as an input, the MCU can read
the port input through the Data In buffer. See Fig-
ure 22.
Ports C and D do not have Control Registers, and
are in MCU I/O mode by default. They can be used
for PLD I/O if equations are written for them in PS-
Dabel.
PLD I/O Mode
The PLD I/O Mode uses a port as an input to the
CPLD’s Input Macrocells (IMC), and/or as an out-
put from the CPLD’s Output Macrocells (OMC).
The output can be tri-stated with a control signal.
This output enable control signal can be defined
by a product term from the PLD, or by resetting the
corresponding bit in the Direction Register to 0.
The corresponding bit in the Direction Register
must not be set to 1 if the pin is defined for a PLD
input signal in PSDabel. The PLD I/O mode is
specified in PSDabel by declaring the port pins,
and then writing an equation assigning the PLD I/
O to a port.
Address Out Mode
For MCUs with a multiplexed address/data bus,
Address Out Mode can be used to drive latched
addresses on to the port pins. These port pins can,
in turn, drive external devices. Either the output
enable or the corresponding bits of both the Direc-
tion Register and Control Register must be set to
a 1 for pins to use Address Out Mode. This must
be done by the MCU at run-time. See Table 20 for
the address output pin assignments on Ports A
and B for various MCUs.
For non-multiplexed 8-bit bus mode, address sig-
nals (A7-A0) are available to Port B in Address Out
Mode.
Note: Do not drive address signals with Address
Out Mode to an external memory device if it is in-
tended for the MCU to Boot from the external de-
vice. The MCU must first Boot from PSD memory
so the Direction and Control register bits can be
set.
PSD834F2V
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