Memory Access Mode; Single-Chip Mode; Mode Pin (Moda); Mode Data - Fujitsu Semiconductor Controller MB89950/950A Hardware Manual

3.8

Memory Access Mode

In the MB89950/950A series, the only memory access mode is the single-chip mode.
I Single-chip mode
In single-chip mode, the device uses internal RAM and ROM only. Therefore, the CPU can access no areas
other than the internal I/O area, RAM area, and ROM area (internal access).
I Mode pin (MODA)
Always set the mode pin, MODA, to V
At reset, reads the mode data and reset vector from internal ROM.
Do not change the mode pin settings, even after completion of the reset (i.e. during normal operation).
Table 3.8-1 "Mode pin setting" lists the mode pin settings.
Table 3.8-1 Mode pin setting
MODA
pin state
I Mode data
Always set the mode data in internal ROM to "00
Address
FFFD
V
Reads the mode data and reset vector from internal ROM.
SS
V
Prohibited settings
CC
Figure 3.8-1 Mode data structure
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
H
Data
00
Other than
00
H
.
SS
Description
" to select single-chip mode.
H
Operation
Selects single-chip mode.
H
Reserved. Do not set this value.
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