Page 26
Epson Research and Development
Vancouver Design Center
S1D13503
Hardware Functional Specification
X18A-A-001-08
Issue Date: 01/01/29
5.2 Summary of Configuration Options
The S1D13503 requires some configuration information on power-up. This information is provided through the SRAM
data lines VD[0...15]. The state of these pins are read on the falling edge of RESET and used to configure the following
options:
Note
The S1D13503 has internal pulldown resistors on these pins and therefore will be pulled down
and read on a logic “0” after RESET. If pullup resistors are required refer to Table 6-3, “Input
Specifications,” on page 27 for pulldown resistor values.
Example: If an ISA bus (no byte swap) with memory segment “A” and I/O location 300h are used, the corresponding
settings of VD15-VD0 would be:
Where x = don’t care; 1 = connected to pull-up resistor; 0 = no pull-up resistor
Table 5-6: Summary of Power On / Reset Options
Pin Name
value on this pin at falling edge of RESET is used to configure:
(1/0)
1 0
VD0
16-bit host bus interface
8-bit host bus interface
VD1
Use direct-mapping for I/O accesses
Use internal index register for I/O accesses
VD2
MC68000 MPU interface
MPU / Bus interface with memory accesses
controlled by a READY (WAIT#) signal
VD3
Swap of high and low data bytes in 16-bit bus
interface
No byte swap of high and low data bytes in
16-bit bus interface
VD12-VD4
Select I/O mapping address bits [9:1].
These nine bits are latched on power-up and are compared to the MPU address bits [9-1]. A
valid I/O cycle combined with a valid address will enable the internal I/O decoder. Therefore,
both types of I/O mapping are limited to even address boundaries to determine either the
absolute or indexed I/O address of the first register. Note that a “valid I/O cycle” includes
IOCS# being toggled low.
VD15-VD13
Select memory mapping address bits [3:1]
These three bits are latched on power-up and are compared to the MPU address bits [19-17]. A
valid memory cycle combined with a valid address will enable the internal memory decoder.
As only the three most significant bits of the address are compared, the maximum amount of
memory supported is 128K bytes. Note that a “valid memory cycle” includes MEMCS# being
toggled low.
When using 128K byte memory it must be mapped at an even address such that all 128K bytes
is available without a change in state on A17, as this would invalidate the internal compare
logic.
Table 5-7: I/O and Memory Addressing Example
8-Bit ISA Bus
16-Bit ISA Bus
Pin Name
Index
Register
Direct Mapping
Index
Register
Direct Mapping
VD0
0
0
1
1
VD1
0
1
0
1
VD2
0
0
0
0
VD3
0
0
0
0
VD12-VD4
11 0000 000
11 0000 xxx
11 0000 000
11 0000 xxx
VD15-VD13
101
101
101
101
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