HD6412373R RENESAS [Renesas Technology Corp], HD6412373R Datasheet - Page 243

• Manufacturer Part Number: HD6412373R
• Description: Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2300 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 6 Bus Controller (BSC)
If areas 2 to 5 are designated as continuous synchronous DRAM space, large-capacity (e.g. 64-
Mbit) synchronous DRAM can be connected. In this case, the CS2, CS3, CS4, and CS5 pins are
used as the RAS, CAS, WE, and CLK signals for the continuous synchronous DRAM space. The
OE pin is used as the CKE signal.
Area 6: In externally expanded mode, all of area 6 is external space.
When area 6 external space is accessed, the CS6 signal can be output.
Only the basic bus interface can be used for area 6.
Area 7: Area 7 includes the on-chip RAM and internal/O registers. In externally expanded mode,
the space excluding the on-chip RAM and internal I/O registers is external address space. The on-
chip RAM is enabled when the RAME bit is set to 1 in the system control register (SYSCR); when
the RAME bit is cleared to 0, the on-chip RAM is disabled and the corresponding addresses are in
external address space.
When area 7 external address space is accessed, the CS7 signal can be output.
Only the basic bus interface can be used for the area 7 memory interface.
6.4.4
Chip Select Signals
This LSI can output chip select signals (CS0 to CS7) for areas 0 to 7. The signal outputs low when
the corresponding external space area is accessed. Figure 6.7 shows an example of CS0 to CS7
signals output timing.
Enabling or disabling of CS0 to CS7 signals output is set by the data direction register (DDR) bit
for the port corresponding to the CS0 to CS7 pins.
In expanded mode with on-chip ROM disabled, the CS0 pin is placed in the output state after a
reset. Pins CS1 to CS7 are placed in the input state after a reset and so the corresponding DDR bits
should be set to 1 when outputting signals CS1 to CS7.
In expanded mode with on-chip ROM enabled, pins CS0 to CS7 are all placed in the input state
after a reset and so the corresponding DDR bits should be set to 1 when outputting signals CS0 to
CS7.
When areas 2 to 5 are designated as DRAM space, outputs CS2 to CS5 are used as RAS signals.
When areas 2 to 5 are designated as continuous synchronous DRAM space in the H8S/2378R
Group, outputs CS2, CS3, CS4, and CS5 are used as RAS, CAS, WE, and CLK signals.
Rev.7.00 Mar. 18, 2009 page 175 of 1136
REJ09B0109-0700