psd4235g2 STMicroelectronics, psd4235g2 Datasheet - Page 82

• Manufacturer Part Number: psd4235g2
• Description: Flash In-system Programmable Isp Peripherals For 16-bit Mcus 5v Supply
• Manufacturer: STMicroelectronics

I/O ports
20.3
20.4
20.5
Note:
Table 39.
82/129
MCU I/O
PLD I/O
McellA outputs
McellB outputs
Additional Ext. CS outputs
PLD inputs
Address Out
Port Mode
MCU I/O mode
In the MCU I/O mode, the MCU uses the PSD Ports 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
A port pin can be put into MCU I/O mode by writing a ’0’ to the corresponding bit in the
Control register (for Ports E, F and G). 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
Section 20.2: Port operating
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
Ports A, B and C do not have Control registers, and are in MCU I/O mode by default. They
can be used for PLD I/O if they are specified in PSDsoft Express.
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 output 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
PSDsoft Express. The PLD I/O mode is specified in PSDsoft Express by declaring the port
pins, and then specifying an equation in PSDsoft Express.
Address Out mode
For MCUs with a multiplexed address/data bus, Address Out mode can be used to drive
latched addresses onto the port pins. These port pins can, in turn, drive external devices.
Either the output enable or the corresponding bits of both the Direction 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
for various MCUs.
Do not drive address signals with Address Out Mode to an external memory device if it is
intended for the MCU to Boot from the external device. The MCU must first Boot from PSD
memory so the Direction and Control register bits can be set.
Port operating modes
Port A
Yes
Yes
Yes
No
No
No
Table 41
Port B
Yes
Yes
Yes
Yes
No
No
modes). When the pin is configured as an output, the content of
for the address output pin assignments on Ports E, F and G
Table
Port C
Yes
Yes
Yes
No
No
No
6.
Figure
Port D
Yes
Yes
No
No
No
No
26).
Yes (A7 - 0) Yes (A7 - 0)
Port E
Yes
No
No
No
No
Port F
Yes
Yes
Yes
No
No
PSD4235G2
Yes (A7 - 0)
or (A15 - 8)
Port G
Yes
No
No
No
No