AMD Am79C930 - Manual (Page 59)

P R E L I M I N A R Y AMD
59 Am79C930
Am79C930 Device PCMCIA Mode Resource Requirements
Common Common Attribute Attribute
Memory Range Memory Size I/O Range I/O Size Memory Range Memory Size
0000h – 7FFFh 32 Kbytes 0000h – 0027h 40 0000h – 0803h 2 K+4 bytes
OR OR OR
0 bytes 0000h – 000Fh 16
bytes
The I/O range is adjusted through bit 2 (EIOW = Expand
I/O Window) of SIR1 = Bank Switching Select register).
Note that since the Am79C930 device’s memory
mapped resources are all accessible through the Local
Memory Address Register and I/O Data Ports
(SIR2,3,4,5,6,7), it is possible to assign the Am79C930
device no memory space. (This is accomplished by
setting the MemSpace field of the TPCE_FS byte of
the Configuration Table Entry Tuple to 00b. This will
inform the PCMCIA configuration utility that the
Am79C930-based design does not require any Com-
mon Memory space.) By assigning
no memory space to
the Am79C930 device, the Am79C930 device will
become an I/O only device. Such an arrangement may
be convenient for systems in which there is not enough
total available memory space to allow the Am79C930
device to use a full 32K block of memory.
Note that when this option is chosen, the total amount of
bus bandwidth required to perform all of the necessary
accesses to the Am79C930-based design will be in-
creased somewhat, because of the indirect nature of the
I/O method of access to Am79C930-based resources.
Note that the Am79C930 device always decodes
the lowest 6 bits of address when an I/O access is
performed with the Am79C930 device’s CE1 signal ac-
tive. This means that there is aliasing of addresses in I/O
space. This decode function is unaffected by the setting
of the SIR1[2:0] register bits.
PCMCIA Common Memory Resources — While the
common memory space of the Am79C930 device only
accommodates access to 32 Kbytes of memory, the
Am79C930 device uses device select and bank select
bits in SIR1 in order to access a total of 256K of memory
space. Note that PCMCIA accesses to Common mem-
ory locations 7C00h–7FFFh (1K total space) will
some-
times correspond to the same physical locations as
PCMCIA accesses to Attribute memory locations
0000h–07FFh (2K total space), i.e., the correspon-
dence will occur only when the device and bank select
bits of SIR1 are pointing at the upper page of the 128K
Flash memory address space. (Note that for Attribute
memory accesses, only the even-valued addresses are
defined to exist. Therefore, 2K total Attribute memory
addresses have been mapped to 1K of physical space in
the Flash memory.) The following table indicates the
mapping of the 256 Kbytes of physical memory space
into the 32 Kbytes of Common memory:
Am79C930 Device PCMCIA Mode Common Memory Map
PCMCIA Address in
Common Memory SIR1[5:3] Size of Space Physical Memory
0000h – 7FFFh 000 32 Kbytes SRAM Memory 0 0000h – 0 7FFFh
0000h – 7FFFh 001 32 Kbytes SRAM Memory 0 8000h – 0 FFFFh
0000h – 7FFFh 010 32 Kbytes SRAM Memory 1 0000h – 1 7FFFh
0000h – 7FFFh 011 32 Kbytes SRAM Memory 1 8000h – 1 FFFFh
0000h – 7FFFh 100 32 Kbytes Flash Memory 0 0000h – 0 7FFFh
0000h – 7FFFh 101 32 Kbytes Flash Memory 0 8000h – 0 FFFFh
0000h – 7FFFh 110 32 Kbytes Flash Memory 1 0000h – 1 7FFFh
0000h – 7FFFh 111 32 Kbytes Flash Memory 1 8000h – 1 FFFFh
TOTAL: 256 Kbytes