C8051F388 Datasheet, PDF (95/285 Pages) –

C8051F388/9/A/B
14.5.3. Split Mode with Bank Select
When EMI0CF.[3:2] are set to 10, the XRAM memory map is split into two areas, on-chip space and
off-chip space.
 Effective addresses below the internal XRAM size boundary will access on-chip XRAM space.
 Effective addresses above the internal XRAM size boundary will access off-chip space.
 8-bit MOVX operations use the contents of EMI0CN to determine whether the memory access is
on-chip or off-chip. The upper 8-bits of the Address Bus A[15:8] are determined by EMI0CN, and the
lower 8-bits of the Address Bus A[7:0] are determined by R0 or R1. All 16-bits of the Address Bus
A[15:0] are driven in “Bank Select” mode.
 16-bit MOVX operations use the contents of DPTR to determine whether the memory access is on-chip
or off-chip, and the full 16-bits of the Address Bus A[15:0] are driven during the off-chip transaction.
14.5.4. External Only
When EMI0CF[3:2] are set to 11, all MOVX operations are directed to off-chip space. On-chip XRAM is not
visible to the CPU. This mode is useful for accessing off-chip memory located between 0x0000 and the
internal XRAM size boundary.
 8-bit MOVX operations ignore the contents of EMI0CN. The upper Address bits A[15:8] are not driven
(identical behavior to an off-chip access in “Split Mode without Bank Select” described above). This
allows the user to manipulate the upper address bits at will by setting the Port state directly. The lower
8-bits of the effective address A[7:0] are determined by the contents of R0 or R1.
 16-bit MOVX operations use the contents of DPTR to determine the effective address A[15:0]. The full
16-bits of the Address Bus A[15:0] are driven during the off-chip transaction.
Rev. 1.1
95