CS8920A View Datasheet(PDF) - Cirrus Logic
Part Name
Description
MFG CO.
'CS8920A' PDF : 144 Pages View PDF
CS8920A
EEPROM address of the checksum value can be
determined by dividing the value stored in the
Link Byte by two). The checksum value is the
2’s complement of the 8-bit sum (any carry out
of eighth bit is ignored) of all the bytes in the
Reset Configuration Block, excluding the check-
sum byte. This sum includes the Reset
Configuration Block header at address 00h.
Since the checksum value is calculated as the 2’s
complement of the sum of all the preceding
bytes in the in the Reset Configuration Block, a
total of 0 should result when the checksum value
is added to the sum of the previous bytes.
EEPROM Example
Table 3.6 shows an example of a Reset Configu-
ration Block stored in a ’C56 (non-sequential)
EEPROM. The B112h value in the header dis-
ables Plug and Play support and specifies
eighteen bytes of configuration data follow.
Note that little-endian word ordering is used, i.e.,
the least significant word of a multi-word datum
is located at the lowest address.
EEPROM Readout
If the EEDI pin is asserted high at the end of
reset, the CS8920A reads the first word of
EEPROM data by:
1. Asserting EECS
2. Clocking out a Read-Register-00h command
on EEDO (EESK provides a 1 MHz serial clock
signal)
3. Clocking the data in on EEDI.
If the EEDI pin is low at the end of the reset
signal, the CS8920A does not perform an
EEPROM readout (uses its default configura-
tion).
Determining EEPROM Size: The CS8920A de-
termines the size of the EEPROM by checking
the sense of EEDI on the tenth rising edge of
EESK. If EEDI is low, the EEPROM is a ’C46
or ’CS46. If EEDI is high, the EEPROM is a
’C56, ’CS56, ’C66, or ’CS66.
Loading Configuration Data: The CS8920A
reads in the first word from the EEPROM to de-
termine if configuration data are contained in the
AD7 - AD0 used with ’C56,
’CS56, ’C66 and ’CS66
F EDCB A
9876543210
X X X X X ELSEL OB1 OB0 AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0
Bit
[F:B]
[A]
[9:8]
[7:0]
Name
ELSEL
OB1, OB0
AD7 to AD0
AD5 - AD0 used with
’C46 and ’CS46
Description
Reserved
External Logic Select: When clear, the EECS pin is used to select the EEPROM. When set,
the ELCS pin is used to select the external LA decode circuit.
Opcode: Indicates what command is being executed (see next section).
EEPROM Address: Address of EEPROM word being accessed.
Figure 3.2. EEPROM Command Register Format
22
DS238PP2
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