XR21B1420IL28-0A Datasheet, PDF (40/60 Pages) Exar Corporation – Enhanced 1-Ch Full-Speed USB UART

XR21B1420
OTP Memory Descriptions
Some OTP locations will be pre-programmed at the factory. All OTP reset default values are ’0’ indicating that these bits
have not been programmed. Conversely a ’1’ in any bit position indicates that bit has been previously programmed.
NOTE: The contents of all fields, except the CDC_ACM overrides fields will not take effect unless the corresponding bit in
the PROG_BYTE_LSB or PROG_BYTE_MSB registers have been set. Once that bit has been set, no further changes can
be made to that field. CAUTION: Do not set the PROG bit for any field that has not had desired data entered, otherwise, the
field will be programmed with all ’0’s.
HW_CONFIG (0x000) - Read/Write OTP
Bit
7
6
5:0
Default
Description
0
Reserved
This bit is reserved and should remain ‘0’.
0
Lock
0: Global lock is not set
1: Global lock is set. All further writes to the OTP will be disallowed. Before setting the Global Lock bit, user
must first set register 0x1898 to 0x10. Note that global lock does not take effect until the next hardware or power
on reset.
0
Reserved
Factory programmed - overwriting these bits may cause functional damage to the XR21B1420 device
CDC_ACM_OVERRIDES (0x007) - Read/Write OTP
CDC_ACM override registers 0x008 - 0x00E are not described here as the bit definitions are the same as in the equivalent
register in Table 5.
Bit
7:5
4
3
2
1
0
Default
Description
0
Reserved
These bits are reserved and should be written as ‘0’.
0
BAUD_THRESHOLD
0: Use default CDC-ACM
1: Override CDC-ACM baud rate threshold defaults with the values in the CDC_ACM_BAUD_THRESH regis-
ters
0
GPIO_INT_MASK
0: Use default CDC-ACM
1: Override CDC-ACM GPIO interrupt mask defaults with the values in the CDC_ACM_GPIO_INT_MASK regis-
ter
0
GPIO_DIRECTION
0: Use default CDC-ACM
1: Override CDC-ACM GPIO direction defaults with the values in the CDC_ACM_DIR register
0
GPIO_MODE
0: Use default CDC-ACM
1: Override CDC-ACM GPIO mode defaults with the values in the CDC_ACM_GPIO_MODE register
0
Flow
0: Use default CDC-ACM flow control
1: Override CDC-ACM flow control defaults with the values in the CDC_ACM_FLOW register
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Rev 1A