全称：External Bus Selection Register
Layout：
域定义：CLKOUT, OSCDIS, EMIFX2, SP2, SP1, PP
读写方法：
(a) Macros to read/write CHIP register values
CHIP_RGET() Uint16 CHIP_RGET(REG)
CHIP_RSET() void CHIP_RSET(REG, Uint16 regval)
(b) Macros to read/write CHIP register field values (Applicable only to registers with more than one field)
CHIP_FGET() Uint16 CHIP_FGET(REG, FIELD)
CHIP_FSET() void CHIP_FSET(REG,FIELD, Uint16 fieldval)
(c) Macros to read/write CHIP register field values (Applicable only to registers with more than one field)
CHIP_REG_RMK() Uint16 CHIP_REG_RMK(fieldval_n,...fieldval_0)
Note: *Start with field values with most significant field
positions:
field_n: MSB field
field_0: LSB field
* only writeable fields allowed
CHIP_FMK() Uint16 CHIP_FMK(REG, FIELD, fieldval)
(d) Macros to read a register address
CHIP_ADDR() Uint16 CHIP_ADDR(REG)
Notes: 1) REG indicates the register XBSR
2) FIELD indicates the register field name
For REG_FSET and REG_FMK, FIELD must be a writable field.
For REG_FGET, the field must be a readable field.
3) regval indicates the value to write in the register (REG).
4) fieldval indicates the value to write in the field (FIELD).