![](http://datasheet.mmic.net.cn/330000/PCI6421_datasheet_16443878/PCI6421_181.png)
93
9.3
Command Register
The command register provides control over the Smart Card controller interface to the PCI bus. All bit functions
adhere to the definitions in the
PCI Local Bus Specification
, as seen in the following bit descriptions. The SERR_EN
and PERR_EN enable bits in this register are internally wired-OR between other functions, and these control bits
appear separately according to their software function. See Table 92 for a complete description of the register
contents.
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Name
Command
Type
R
R
R
R
R
RW
R
RW
R
RW
R
R
R
R
RW
R
Default
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Register:
Offset:
Type:
Default:
Command
04h
Read/Write, Read-only
0000h
Table 92. Command Register Description
BIT
FIELD NAME
TYPE
DESCRIPTION
1511
RSVD
R
Reserved. Bits 1511 return 0s when read.
10
INT_DIS
RW
INTx disable. When set to 1, this bit disables the function from asserting interrupts on the INTx signals.
0 = INTx assertion is enabled (default)
1 = INTx assertion is disabled
9
FBB_EN
R
Fast back-to-back enable. The Smart Card interface does not generate fast back-to-back transactions;
therefore, bit 9 returns 0 when read.
8
SER_EN
RW
System error (SERR) enable. Bit 8 controls the enable for the SERR driver on the PCI interface. SERR
can be asserted after detecting an address parity error on the PCI bus. Both bits 8 and 6 (PERR_EN)
must be set for this function to report address parity errors.
0 = Disable SERR output driver (default)
1 = Enable SERR output driver
7
RSVD
R
Reserved. Bit 7 returns 0 when read.
6
PERR_EN
RW
Parity error response enable. Bit 6 controls this function response to parity errors through PERR. Data
parity errors are indicated by asserting PERR, whereas address parity errors are indicated by
asserting SERR.
0 = This function ignores detected parity error (default)
1 = This function responds to detected parity errors
5
VGA_EN
R
VGA palette snoop enable. The Smart Card interface does not feature VGA palette snooping;
therefore, bit 5 returns 0 when read.
4
MWI_EN
R
Memory write and invalidate enable. The Smart Card controller does not generate memory write
invalidate transactions; therefore, bit 4 returns 0 when read.
3
SPECIAL
R
Special cycle enable. The Smart Card interface does not respond to special cycle transactions;
therefore, bit 3 returns 0 when read.
2
MAST_EN
R
Bus master enable. This function is target only.
1
MEM_EN
RW
Memory space enable. This bit controls memory access.
0 = Disables this function from responding to memory space accesses (default)
1 = Enables this function to respond to memory space accesses
0
IO_EN
R
I/O space enable. The Smart Card interface does not implement any I/O-mapped functionality;
therefore, bit 0 returns 0 when read.