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PSD5XX Famly
6-4
General
Description
(Cont.)
At the core of the PSD5XX are dedicated ZPLDs based on the functions they perform:
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Decoding ZPLD (DPLD)
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General Purpose ZPLD (GPLD)
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Peripheral ZPLD (PPLD)
All ZPLDs receive the same inputs through the ZPLD bus and are differentiated by their
output destinations. The Decoder PLD (DPLD ) has as its main function to perform address
space decoding for the internal I/O Ports, Peripherals, four blocks of EPROM, standby
SRAM and peripheral mode of Port A. The address decoding can be based on any address
input, control signal (RD, PSEN, etc.) and page logic. Address inputs originate from either
the microcontroller interface (ADIO Port) or other I/O Ports for additional decoding. The
DPLD also supports special requirements of 8031 architecture based designs that need to
store data in the EPROM or execute programs from the SRAM.
The general purpose PLD (GPLD) is a general purpose ZPLD that can be used to
implement state machines and logic . The GPLD has up to 61 inputs, 118 product terms,
24 flexible macrocells and 24 I/O pins that are connected to Ports A, B and E. The GPLD
can also decode the microcontroller address bus and generate chip selects to external
peripherals or memories.
The peripheral PLD (PPLD) generates outputs to the Counter/Timer unit and the Interrupt
Controller. The PPLD outputs to the Counter/Timer enable, disable or trigger counting or
time capture. This unique capability enables the user to implement in the PPLD the exact
conditions for the timer to count or generate an output. The PPLD also generates four
outputs to the Interrupt Controller which enables the user to define the exact conditions for
interrupt generation.
The ZPLDs are designed to consume minimum power using Zero Power design techniques.
A configuration bit (Turbo bit), that can be set by the MCU, will automatically place the
ZPLDs into standby if no inputs are changing. Any unused product terms will be turned off
during programming and will not consume any power in the system.
The PSD5XX has 40 I/O pins that are divided into 5 ports. Each I/O pin can be individually
configured to provide many functions. Ports A, B and E have the capability to be
configured as standard MCU I/O ports, GPLD I/O, latched address outputs for multiplexed
address/data controllers, or special function I/O (e. g., Counter/Timer and Interrupts).
Ports C and D are standard I/O ports that can also be configured as ZPLD inputs or data
bus for microcontrollers with non-multiplexed bus.
The PSD5XX can easily interface with no “glue-logic” to a variety of 8 and 16-bit
microcontrollers with a multiplexed or non-multiplexed bus. All of the control signals are
connected to the three ZPLDs enabling the user to generate timing and decoding signals for
external peripherals. For controllers that do not have a Reset output, the PSD5XX can
generate a RESET output based on its RESET input that includes hysteresis.
The Counter/Timer unit provides four 16 bit highly flexible Counter/Timers. Each
Counter/Timer has five modes of operation: pulse, waveform, event counting, time capture
and watchdog (Real Time Clock). Counter 2 can operate as a Watch Dog Timer. Each
Counter/Timer can be programmed to count up or down. The inputs to the Counter/Timer
unit, which enable/disable counting or triggering an operation, can originate from the PPLD
or directly from the pins. The maximum operating frequency of each counter is 7.5 MHz.
The input clock can be divided (up to 280) before driving the Counter/Timer unit using the 4
to 280 range prescaler .