Description Of Registers - Nintendo GAME BOY Programming Manual

4.4 Description of Registers

! Register for Specifying External Expansion Memory (RAMG)
Specifies whether external expansion RAM is accessible. Access to this RAM is enabled by
writing 0Ah to the RAMG register space, 0000h-1FFFh. Writing any other value to this register
disables reading to and writing from RAM.
! Lower ROM Bank Register (ROMB0)
Specifies the lower-order 8 bits of a 9-bit ROM bank.
The ROM bank can be changed by writing the desired ROM bank number to the ROMB0
register area, 2000h-2FFFh.
! Upper ROM Bank Register (ROMB1)
Specifies the higher-order 1 bit of a 9-bit ROM bank.
The ROM bank can be changed by writing the desired ROM bank number to the ROMB1
register area, 3000h-3FFFh.
! RAM Bank Register (RAMB)
Specifies the RAM bank
The RAM bank can be changed by writing the desired RAM bank number to the RAMB register
area, 4000h-5FFFh.
Note Although the bits marked with
should be used after being set to 0. The default values are set
automatically when power is turned on.
Chapter 8: Game Boy Memory Controllers (MBC)
are ignored by MBC5, they
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