Chapter 3 Hardware
CoreModule 420 Reference Manual 23
Pin # Signal Description (P1 Row A)
27 (A27) SA4 System Address 4 – Refer to SA19, pin A12, for more information.
28 (A28) SA3 System Address 3 – Refer to SA19, pin A12, for more information.
29 (A29) SA2 System Address 2 – Refer to SA19, pin A12, for more information.
30 (A30) SA1 System Address 1 – Refer to SA19, pin A12, for more information.
31 (A31) SA0 System Address 0 – Refer to SA19, pin A12, for more information.
32 (A32) GND Ground
Notes: The shaded area denotes power or ground. The signals marked with * indicate active low.
Table 3-6. PC/104 Bus Interface Pin/Signal Descriptions (P1B)
Pin # Signal Description (P1 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 +5V power +/- 10%
36 (B4) IRQ9
Interrupt Request 9 – Asserted by a device when it has pending interrupt
request. Only one device may use this request line at a time.
37 (B5) NC(-5V) Not connected (-5 volts)
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) NC(-12V) Not connected (-12 volts)
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 Volts
42 (B10) Key (NC) Key Pin (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.
48 (B16) DRQ3
DMA Request 3 – Used by I/O resources to request DMA service.
Must be held high until associated DACK3 line is active.
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