HD6433308 Datasheet, PDF (240/349 Pages) Hitachi Semiconductor – Hitachi Single-Chip MicroComputer

System Control Register (SYSCR)—H’FFC4
Bit
Initial value
Read/Write
7
SSBY
0
R/W
6
STS2
0
R/W
5
STS1
0
R/W
4
STS0
0
R/W
3
2
1
0
— NMIEG DPME RAME
1
0
0
1
—
R/W R/W R/W
The only bit in the system control register that concerns the dual-port RAM is the DPME bit. See
section 2.4.2, "System Control Register" for the other bits.
Bit 1 – Dual-Port RAM Enable (DPME): This bit enables or disables the dual-port RAM. The
dual-port RAM can be enabled only in the single-chip mode (mode 3).
Bit 1
DPME
0
1
Description
The dual-port RAM is disabled.
The dual-port RAM is enabled (in single-chip mode only).
(Initial value)
If the DPME bit is set to “1” while the H8/330 is operating in the single-chip mode, the following
pins are automatically assigned to dual-port RAM functions, regardless of their data direction
register settings:
Port 3 (P37 to P30) →DDB7 to DDB0 (parallel communication data bus; input/output)
Port 8 (P83 to P80) →RS3 to RS0 (dual-port RAM register select; input)
In port 9, P97 → WE (Write Enable; input)
P95 →RDY (Ready; output)
P94 → OE (Output Enable; input)
P93 → CS (Chip Select; input)
The DPME bit is initialized to “0” by a reset and in the hardware standby mode.
Setting the DPME bit to "1" in the expanded modes (modes 1 and 2) has no effect.
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