ZPSD511B1C15J STMicroelectronics, ZPSD511B1C15J Datasheet - Page 59

• Manufacturer Part Number: ZPSD511B1C15J
• Manufacturer: STMicroelectronics

Specifications of ZPSD511B1C15J

• Operating Temperature (max): 70C
• Operating Temperature (min): 0C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Supplier Unconfirmed

Peripheral I/O
56
PSD5XX Family
Figure 28. Port A In Peripheral I/O Mode
9.4.5 Peripheral I/O
The Peripheral I/O Mode is one of the operating modes of Port A. In this mode, Port A
is connected to the data bus of peripheral devices. Port A is enabled only when the
microcontroller is accessing the devices, otherwise the Port is tri-stated. This feature
enables the microcontroller to access external devices without requiring buffers and
decoders. Figure 28 shows the structure of Port A in the Peripheral I/O Mode.
The memory address space occupied by the devices are defined by two signals: PSEL0
and PSEL1. The signals are direct outputs from the DPLD. Whenever any of the signals is
active, the Port A driver is enabled, and the direction of the data flow is determined by the
RD/WR signals.
The Peripheral I/O Mode and the peripheral select signals are configured and defined in the
PSDsoft Software (see the section on I/O Port for configurations). The PIO bit in the VM
Register (see Table 16) also needs to be set to “1” by the user to initialize the Peripheral I/O
Mode.
The Peripheral I/O mode can be used, for example, in DMA applications where the
microcontroller does not support DMA operations, such as tri-stating the address/data bus.
Figure 29 shows a block diagram of a microcontroller and PSD5XX based design that
makes use of this mode. In this application, the microcontroller has a multiplexed bus which
is connected to the ADIO port. The C and D ports connect to the peripheral address bus
and are both configured in Address Out Mode. Port A is configured in the Peripheral I/O
mode and is connected to the peripheral data bus. Port B and E are used to generate
control signals.
During normal activity, the microcontroller has access to any peripheral (memory or I/O
device) through the PSD5XX device. When there is a DMA request, the microcontroller
tri-states the address bus on Port C and D by writing a “0” to the port Direction Registers.
The DMA controller then takes over the data and address buses after receiving
acknowledgement from the microcontroller.
RD
PSEL0
PSEL1
D0 – D7
WR
PA0 – PA7