
I-42
EPSON
S1C88348/317/316/308 TECHNICAL HARDWARE
5 PERIPHERAL CIRCUITS AND THEIR OPERATION (System Controller and Bus Control)
5.2
System Controller and Bus Control
The system controller is a management unit which
sets such items as the bus mode in accordance with
memory system configuration factors.
For the purposes of controlling the system, the
following settings can be performed in software:
(1) Bus mode (CPU mode) settings
(2) Chip enable (CE) signal output settings
(3) WAIT state settings for external memory
(4) Bus authority release request / acknowledge
signal (BREQ/BACK) settings
(5) Page address setting of the stack pointer
Note: There is no bus authority release function in
the S1C88308.
Below is a description of the how these settings are
to be made.
5.2.1 Bus mode settings
As explained in "3.5.2 Bus mode", the S1C883xx has
four bus modes. Settings for bus modes must be
made in software and must match the capacity of
the external memory.
As shown in Table 5.2.1.1, bus mode settings are
performed on the basis of the preset values for each
mode written to the registers BSMD0 and BSMD1.
Table 5.2.1.1 Bus mode settings
*
The single chip mode setting is only possible
when this IC is used in the MCU mode. The
single chip mode setting is incompatible with
the MPU mode, since this mode does not utilize
internal ROM.
When using in the MPU mode, it is necessary to
select the bus mode at the time of the initial
resetting and at the time of the <BSMD1 = "0"
and BSMD0 = "0"> setting from among the three
types of expanded modes (expanded 64K mode,
expanded 512K minimum mode and expanded
512K maximum mode) by mask option.
Select the expanded 512K maximum mode for
this option, when the MPU mode is not used at
all.
BSMD1
1
0
ROM+RAM
>64K bytes (Program>64K bytes)
ROM+RAM
>64K bytes (Program≤64K bytes)
ROM+RAM
≤64K bytes
None
See above
Expanded 512K maximum mode
Expanded 512K minimum mode
Expanded 64K mode
Single chip mode (MCU)
Optional setting of one of the expanded
modes (MPU)
Setting value
Bus mode
Configuration of external memory
BSMD0
1
0
1
0