400
CY8C28xxx PSoC Programmable System-on-Chip TRM, Document No. 001-52594 Rev. *G
Analog Interface
register is written with the new value within a few CPU
clocks after PHI1.
The rising edge of PHI1 is also the optimal time to write the
DAC register for maximum settling time. The timing from the
positive edge of PHI1 to the start of the I/O write is 4.5
clocks, which at 24 MHz is 189 ns. If the analog clock is run-
ning at 1 MHz, this allows over 300 ns for the DAC output
and comparator to settle.
Figure 18-7. General SAR Timing
18.3
Register Definitions
The following registers are associated with the Analog Interface and are listed in address order. Each register description has
an associated register table showing the bit structure for that register. For a complete table of analog interface registers, refer
to the
“Summary Table of the Analog Registers” on page 389
.
Depending on how many analog columns your PSoC device has (see the Cols. column in the register tables below), only cer-
tain bits are accessible to be read or written (refer to the table titled
“PSoC Device Characteristics” on page 387
). The bits that
are grayed out throughout this manual are reserved bits and are not detailed in the register descriptions that follow. Reserved
bits should always be written with a value of ‘0’.
18.3.1
CLK_CR3 Register
The Analog Clock Source Control Register 3 (CLK_CR3) is
used to select the clock source for an individual analog col-
umn.
Bits 3 to 0: SYSDIR[3:0] .
When the corresponding bit is 1,
then the associated ACC column's clock source is SYSCLK.
Otherwise it follows the setting of the CLK_CR0 register.
For additional information, refer to the
.
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
0,62h
SYSDIR[3:0] RW : 00
PHI1
PHI2
ACMP
IOR
IOW
STALL
Comparator is valid on PHI1
rising. SAR computation is
done and IOR finishes.
DAC output is valid
at end of PHI2.
Comparator is now
valid for previous IOW,
repeat process.
IOR causes STALL
to assert, to wait for
PHI1 rising.
New value is written
to DAC register.
Summary of Contents for CY8C28 series
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