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AMD
79Am79C930
SIR2: Local Memory Address Register [7:0] (LMA)
This register is the beginning address on the local bus
for system interface I/O transfers that are made to the
I/O Data Port. This register automatically increments by
“1” following each read or write operation of any section
of the I/O Data Port. (MA[16:15] will be given the values
of BSS[4:3] – memory bank select bits.)
Bit Name Reset Value Description
7:0 LMA[7:0] – These 8 bits act as Am79C930 memory interface bus address bits
MA[7:0] during system interface accesses to Flash and SRAM
whenever any section of the I/O Data port is read or written. The
LMA[14:0] value is automatically incremented by R1S after any
section of the I/O Data Port is read or written.
Note that these bits are unaffected by any RESET operation.
SIR3: Local Memory Address Register [14:8] (LMA)
This register is the beginning address on the local bus
for system interface I/O transfers that are made to the
I/O Data Port. This register automatically increments by
“1” following each read or write operation of any of the
I/O Data Ports in which the LMA [7:0] register produces
a carry out from bit LMA[7].
Bit Name Reset Value Description
7 ISAPWRDWN 0 Requests the 80188 to enter power down mode if the device is op-
erating in the ISA Plug and Play mode. If already in power down
mode, this bit will indicate 1. If written with a 0 while in power down
mode, power down mode is exited. When written with a 1, value
read will remain 0 until the device actually enters the power down
mode. When written with a 1, the PWRDWN bit generates an inter-
rupt to the 80188, requesting that the 80188 core place the
Am79C930 device into the power down state. The interrupt is sig-
naled in MIR0, bit 5. The PWRDWN bit of SIR3 is identical in func-
tion to the PCMCIA Card Configuration and Status Register’s
Power Down bit, but this bit is only functional when the ISA Plug and
Play mode has been selected. This bit is reserved and should be
written as 0 when the PCMCIA mode of operation has been
selected. Reads of this bit produce undefined data when in
PCMCIA mode.
6:0 LMA[14:8] – These seven bits act as Am79C930 memory interface bus address
bits MA[14:8] during system interface accesses to Flash and SRAM
whenever any section of the I/O Data port is read or written. The
LMA[14:0] value is automatically incremented by “1” after any of the
I/O Data Ports is read or written. (Note that MA[16:15] will be given
the values of SIR1[4:3] – memory bank select bits.)
Note that these bits are unaffected by any RESET operation.
SIR4: I/O Data Port A (IODPA)
This register directly accesses the Am79C930 memory
interface data bus at the memory interface bus address
specified by the current value of the LMA registers and
the SIR1[5:3] bits. Each read or write operation of any of
the I/O Data Ports causes an increment of “1” to the LSB
of the LMA. All four I/O Data Ports will use the same
LMA and SIR1[5:3] values. That is, each I/O Data Port is
equivalent to the others, except for their location in sys-
tem I/O space. Different I/O Data Ports do not imply a
built in offset of LMA values.
Bit Name Reset Value Description
7:0 IODPA[7:0] – These eight bits act as Am79C930 memory interface bus data bits
MD[7:0] during system interface accesses to Flash and SRAM
whenever any section of the I/O Data port is read or written.