XR21B1422IL40-0A Datasheet, PDF (42/60 Pages) Exar Corporation – Enhanced 2-Ch Full-Speed USB UART

XR21B1422
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 reg-
ister 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 XR21B1422 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 registers
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 register
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
© 2014 Exar Corporation
42 / 60
exar.com/XR21B1422
Rev 1A