zpsd211r STMicroelectronics, zpsd211r Datasheet - Page 27

• Manufacturer Part Number: zpsd211r
• Description: Low Cost Field Programmable Microcontroller Peripherals
• Manufacturer: STMicroelectronics

16.
Power
Management
(cont.)
24
PSD211R Family
16.3 Turbo Bit (ZPSD only)
The turbo bit is controlled by the MCU at run-time and is accessed through bit zero of the
Power Management Register (PMR). The PMR is located in CSIOPORT space at offset 10h.
*
Power Management Register (PMR)
The default value at reset of all bits in the PMR is logic 0, which means the Turbo feature is
enabled. The PAD logic (PAD A and PAD B) of the PSD will operate at full speed and full
power. When the Turbo bit is set to logic 1, the Turbo feature is disabled. When disabled,
the PAD logic will draw only standby current (micro-amps) while no PAD inputs change.
Whenever there is a transition on any PAD input (including MCU address and control
signals), the PAD logic will power up and will generate new outputs, latch those outputs,
then go back to Standby Mode. Keep in mind that the signal propagation delay through
the PAD logic increases by 10 nsec for non-V devices, and 20 nsec for V devices while in
non-turbo mode. Use of the Turbo bit does not affect the operation or power consumption of
memory.
Tremendous power savings are possible by setting the Turbo bit and going into non-turbo
mode. This essentially reduces the DC power consumption of the PAD logic to zero. It also
reduces the AC power consumption of PAD logic when the composite frequency of all PAD
inputs change at a rate less than 40 MHz for non-V devices, and less than 20 MHz for V
devices. Use figures 13 and 14 to calculate AC and DC current usage in the PAD with the
Turbo bit on and off. You will need to know the number of product terms that are used in
your design and you will have to calculate the composite frequency of all signals entering
the PAD logic.
16.4 Number of Product Terms in the PAD Logic
The number of product terms used in your design relates directly to how much current the
PADs will draw. Therefore, minimizing this number will be in your best interest if power is a
concern for you. Basically, the amount of product terms your design will use is based on the
following (see Figure 4):
Given the above product term allocation, keep the following three points in mind when
calculating the total number of product terms your design will require:
1) The EPROM block selects and CSIOPORT select will use a product term whether you
2) For Port B, if you use a pin as an output and your logic equation requires only one
3) The following PSD functions do not consume product terms: MCU I/O mode, Latched
Future Configuration bits are reserved and should be set to one when writing to this register.
1= OFF
•
•
•
•
•
use these blocks or not. This means you start out with 9 product terms, and go up from
there.
product term, you still have to include all the available product terms for that pin for
power consumption, even though only one product term is specified. For example, if the
output equation for pin PB0 uses just one product term, you will have to count PB0 as
contributing four product terms to the overall count. With this in mind, you should use
Port C for the outputs that only require one product term and PB4-7 for outputs that
require two product terms. Use pins PB0-3 if you need outputs requiring more than two
product terms or you have run out of outputs.
Address Output, and PAD inputs (logic or address).
Bit 7
Each of the EPROM block selects, ES0-ES7 uses one product term (for a total of 8).
The CSIOPORT select uses one product term.
Port B, pins PB0-PB3 are allocated four product terms each if used as outputs.
Port B, pins PB4-PB7 are allocated two product terms each if used as outputs.
Port C, pins PC0-PC2 are allocated one product term each if used as outputs.
*
1= OFF
Bit 6
*
1= OFF
Bit 5
*
1= OFF
Bit 4
*
1= OFF
Bit 3
*
1= OFF
Bit 2
*
1= OFF
Bit 1
*
Turbo bit
1= OFF
Bit 0