CY7C68310
Document 38-08030 Rev. *H
Page 26 of 34
6.3
Programming the EEPROM
Programming of the I2C memory device can be accomplished
using an external device programmer, CY7C68310 supported
vendor-specific USB commands, or an in-system programmer
such as a bed of nails. Table 6-3 shows the format of the
vendor-specific commands used to program the EEPROM via
USB. Any vendor-specific USB write request to the Serial
ROM device configuration space will simultaneously update
internal configuration register values as well. If the I2C device
is programmed without vendor specific USB commands,
CY7C68310 must be synchronously reset (nRESET) before
configuration data is reloaded.
The CY7C68310 supports a subset of the “slow mode” speci-
fication (100 KHz) required for 24LCXXB EEPROM family
device support. Features such as “Multi-Master,” “Clock
Synchronization” (the SCL pin is output only), “10-bit
addressing,” and “CBUS device support” are not supported.
Vendor-specific USB commands allow the CY7C68310 to
address
up
to
2
Kbytes
of
data
(although
configu-
ration/descriptor information is limited to 512 bytes of register
space).
6.3.1
LOAD_CONFIG_DATA
This request enables configuration data writes to the data
source specified by the wValue field. The wIndex field
specifies the starting address and the wLength field denotes
the data length in bytes.
Legal values for wValue are as follows:
• 0x0000 Configuration bytes, address range 0x2 – 0xF
• 0x0002 External I2C memory device.
Configuration byte writes must be constrained to addresses
0x2 through 0xF, as shown in Table 6-2. Attempts to write
outside this address space will result in a STALL condition.
Configuration byte writes only overwrite CY7C68310 Configu-
ration Byte registers, the original data source remains
unchanged (I2C-compatible memory device, FBh identify data,
or internal ROM).
Single byte writes to the I2C-compatible memory devices can
start at any address. Writes greater then a single byte must
only start on eight-byte boundaries, meaning that the address
value must be evenly divisible by eight. Writes to I2C-
compatible memory devices must not cross 256-byte page
boundaries, i.e., start and finish write addresses must have
equal modulo 256 values. Write operations with beginning and
end addresses that do not fall in the same 256-byte page will
result in a STALL condition. Illegal values for wValue as well
as attempts to write to an I2C-compatible memory device when
none is connected will result in a STALL condition.
6.3.2
READ_CONFIG_DATA
This USB request allows data retrieval from the data source
specified by the wValue field. Data is retrieved beginning at the
address specified by the wIndex field. The wLength field
denotes the length in bytes of data requested from the data
source.
Legal values for wValue are as follows:
• 0x0000
Configuration bytes, addresses 0x0 – 0xF only
• 0x0001 Internal ROM
• 0x0002 External I2C-compatible memory device
• 0x0003
Vendor-specific identify (FBh) data
Illegal values for wValue will result in a STALL condition on the
USB port. Attempted reads from an I2C-compatible memory
device when none is connected or attempted reads from FBh
data when not in IMODE will result in a STALL condition.
Attempts to read configuration bytes with starting addresses
greater than 0xF will also result in a STALL condition.
0xFC
bString
Unicode character LSB.
0xXX
0xFD
bString
Unicode character MSB.
0x00
0xFE
bString
Unicode character LSB.
0xXX
0xFF
bString
Unicode character MSB.
0x00
Table 6-2. EEPROM Organization (continued)
I2C
Address
Field Name
Field Description
Required
I2C Data
Example
I2C Data
Table 6-3. EEPROM-related Vendor-specific Commands
Label
bmRequestType bRequest
wValue
wIndex
wLength
Data
LOAD_CONFIG_DATA
0x40
0x01
Data Destination Starting Address
Data Length
Configuration
Data
READ_CONFIG_DATA
0xC0
0x02
Data Source
Starting Address
Data Length
Configuration
Data
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