CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
351
Digital Blocks
17.2.1.4
PWMDBL Register Definitions
There are three 8-bit Data registers and two Control registers (a 7-bit and an 8-bit).
explains the meaning of these
registers in the context of the PWMDBL operation. The Control registers are described beginning with section
Note
Read DR0 (to transfer DR0 data to DR2) only when the block is disabled.
17.2.1.5
CRCPRS Register Definitions
There are three 8-bit Data registers and two Control registers (a 7-bit and an 8-bit).
explains the meaning of these
registers in the context of CRCPRS operation. Note that in the CRCPRS function a write to the DR2 Seed register is also
loaded simultaneously into DR0. The Control registers are described beginning with section
.
Table 17-14. PWMDBL Data Register Descriptions
Name
Function
Description
DR0
Count Value
Not directly readable or writeable.
During normal operation, DR0 stores the current count of a synchronous down counter.
When disabled, a write to the DR1 period register is also simultaneously loaded into DR0 from the data bus.
When disabled, a read of DR0 returns 00h to the data bus and transfers the contents of DR0 to DR2. This register should not
be read when the counter is enabled and counting.
DR1
Period
Write only register.
Data in this register sets the period of the count. The actual number of clocks counted is 1.
A period of 00h gives a constant logic high on the auxiliary output.
When disabled, a write to this register also transfers the period value directly into DR0.
When enabled, if the block frequency is 24 MHz or below, this register may be written to at any time, but the period will only
be reloaded into DR0 in the clock following a TC. If the block frequency is 48 MHz, the Terminal Count or Compare Interrupt
should be used to synchronize the new period register write; otherwise, the counter can be incorrectly loaded.
DR2
Compare
Read write register.
DR2 functions as a Compare register.
When enabled, the compare output is computed using the compare type (set in the function register mode bits) between
DR0 and DR2. The result of the compare is output to the primary output.
When disabled, a read of DR0 will transfer the contents of DR0 into DR2.
DR2 may be written to when the function is enabled or disabled.
When counter is running, the data written to DR2 is stored first, then transferred to DR2 register when DR0 is being
reloaded.
Table 17-15. CRCPRS Register Descriptions
Name
Function
Description
DR0
LFSR
Not directly readable or writeable.
During normal operation, DR0 stores the state of a synchronous Linear Feedback Shift register.
When disabled, a write to the DR2 Seed register is also simultaneously loaded into DR0 from the data bus.
In KILL-Reload mode DR2 seed data is loaded into DR0 at each rising edge of block clock when KILL is asserted.
When disabled, a read of DR0 returns 00h to the data bus and transfers the contents of DR0 to DR2. This register should not
be read while the block is enabled.
DR1
Polynomial
Write only register.
Data in this register sets the polynomial for the CRC or PRS function.
Exception
: This register must only be written when the block is disabled.
DR2
Seed/Residue
Read write register.
DR2 functions as a Seed and Residue register.
When disabled, a write to this register also transfers the seed value directly into DR0.
When enabled, DR2 may be written to at any time. The value written will be used in the Compare function.
When enabled, the compare output is computed using the compare type (set in the function register mode bits) between
DR0 and DR2. The result of the compare is output to the auxiliary output.
When disabled, a read of DR0 will transfer the contents of DR0 into DR2. This feature can be used to read out the residue,
after a CRC operation is complete.
Summary of Contents for CY8C28 series
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