Specifications

Chapter 3 Hardware
30 Reference Manual LittleBoard 800
Pin # Signal Description (J1 Row A)
25 (A25) SA6 System Address 6 – Refer to pin-A12 , for more information.
26 (A26) SA5 System Address 5 – Refer to pin-A12 , for more information.
27 (A27) SA4 System Address 4 – Refer to pin-A12 , for more information.
28 (A28) SA3 System Address 3 – Refer to pin-A12 , for more information.
29 (A29) SA2 System Address 2 – Refer to pin-A12 , for more information.
30 (A30) SA1 System Address 1 – Refer to pin-A12 , for more information.
31 (A31) SA0 System Address 0 – Refer to pin-A12 , for more information.
32 (A32) GND Ground
Notes: The shaded area denotes power or ground. The signals marked with * = Negative true logic.
Table 3-6. PC/104 Interface Pin/Signal Descriptions (J1B)
Pin # Signal Descriptions (J1 Row B)
33 (B1) GND Ground
34 (B2) RSTDRV Reset Drive – This signal is used to reset or initialize system logic on
power up or subsequent system reset.
35 (B3) +5V +5 volts ±5% power supply input
36 (B4) IRQ9 Interrupt Request 9 – Asserted by a device when it has a pending interrupt
request. Only one device may use this request line at a time.
37 (B5) -5V -5V volt power (Supplied externally or through PC/104 bus)
38 (B6) DRQ2 DMA Request 2 – Used by I/O resources to request DMA service, or to
request ownership of the bus as a bus master device. Must be held high
until associated DACK2 line is active.
39 (B7) -12V -12 volt power (Supplied externally or through PC/104 bus)
40 (B8) ZWS
Zero Wait State – This signal is driven low by a bus slave device to indicate
it is capable of performing a bus cycle without inserting any additional wait
states. To perform a 16-bit memory cycle without wait states, this signal is
derived from an address decode.
41 (B9) +12V +12 volt power supply input (Supplied externally or through PC/104 bus)
42 (B10) NC Not connected
43 (B11) SMEMW*
System Memory Write – This signal is used by bus owner to request a
memory device to store data currently on the data bus and only active for
the lower 1MB. Used for legacy compatibility with 8-bit cards.
44 (B12) SMEMR* System Memory Read – This signal is used by bus owner to request a
memory device to drive data onto the data bus and only active for lower
1MB. Used for legacy compatibility with 8-bit cards.
45 (B13) IOW* I/O Write – This strobe signal is driven by the owner of the bus (ISA bus
master or DMA controller) and instructs the selected I/O device to capture
the write data on the data bus.
46 (B14) IOR* I/O Read – This strobe signal is driven by the owner of the bus (ISA bus
master or DMA controller) and instructs the selected I/O device to drive
read data onto the data bus.
47 (B15) DACK3* DMA Acknowledge 3 – Used by DMA controller to select the I/O resource
requesting the bus, or to request ownership of the bus as a bus master
device. Can also be used by the ISA bus master to gain control of the bus
from the DMA controller.