R
Platform Flash In-System Programmable Configuration PROMS
grammed to prevent inadvertent writing via JTAG.
and
show the security settings available for the
XCFxxS PROM and XCFxxP PROM, respectively.
Write Protection
The XCFxxP PROM device also allows the user to write
protect (or lock) a particular design revision to prevent inad-
vertent erase or program operations. Once set, the write
protect security bit for an individual design revision must be
reset (using the UNLOCK command followed by
ISC_ERASE command) before an erase or program opera-
tion can be performed.
Table 4:
XCFxxS Device Data Security Options
Read Protect
Reset (default)
Set
√
Read/Verify
Inhibited
Program
Inhibited
Erase
Inhibited
Read Protection
The read protect security bit can be set by the user to pre-
vent the internal programming pattern from being read or
copied via JTAG. Read protection does not prevent write
operations. For the XCFxxS PROM, the read protect secu-
rity bit is set for the entire device, and resetting the read pro-
tect security bit requires erasing the entire device. For the
XCFxxP PROM the read protect security bit can be set for
individual design revisions, and resetting the read protect
bit requires erasing the particular design revision.
Table 5:
XCFxxP Design Revision Data Security Options
Read Protect
Reset (default)
Reset (default)
Set
Set
Write Protect
Reset (default)
Set
Reset (default)
Set
√
√
√
√
√
√
Read/Verify
Inhibited
Program
Inhibited
Erase Inhibited
IEEE 1149.1 Boundary-Scan (JTAG)
The Platform Flash PROM family is IEEE Standard 1532
in-system programming compatible, and is fully compliant
with the IEEE Std. 1149.1 Boundary-Scan, also known as
JTAG, which is a subset of IEEE Std. 1532 Boundary-Scan.
A Test Access Port (TAP) and registers are provided to sup-
port all required boundary scan instructions, as well as
many of the optional instructions specified by IEEE Std.
1149.1. In addition, the JTAG interface is used to implement
in-system programming (ISP) to facilitate configuration, era-
sure, and verification operations on the Platform Flash
PROM device.
Table 6
lists the required and optional
boundary-scan instructions supported in the Platform Flash
PROMs. Refer to the IEEE Std. 1149.1 specification for a
complete description of boundary-scan architecture and the
required and optional instructions.
XCFxxS Instruction Register (8 bits wide)
The Instruction Register (IR) for the XCFxxS PROM is eight
bits wide and is connected between TDI and TDO during an
instruction scan sequence. The detailed composition of the
instruction capture pattern is illustrated in
Figure 4.
The
instruction capture pattern shifted out of the XCFxxS device
includes IR[7:0]. IR[7:5] are reserved bits and are set to a
logic "0". The ISC Status field, IR[4], contains logic "1" if the
device is currently in In-System Configuration (ISC) mode;
otherwise, it contains logic "0". The Security field, IR[3],
contains logic "1" if the device has been programmed with
the security option turned on; otherwise, it contains logic
"0". IR[2] is unused, and is set to '0'. The remaining bits
IR[1:0] are set to '01' as defined by IEEE Std. 1149.1.
XCFxxP Instruction Register (16 bits wide)
Instruction Register
The Instruction Register (IR) for the Platform Flash PROM
is connected between TDI and TDO during an instruction
scan sequence. In preparation for an instruction scan
sequence, the instruction register is parallel loaded with a
fixed instruction capture pattern. This pattern is shifted out
onto TDO (LSB first), while an instruction is shifted into the
instruction register from TDI.
The Instruction Register (IR) for the XCFxxP PROM is six-
teen bits wide and is connected between TDI and TDO dur-
ing an instruction scan sequence. The detailed composition
of the instruction capture pattern is illustrated in
Figure 5.
The instruction capture pattern shifted out of the XCFxxP
device includes IR[15:0]. IR[15:9] are reserved bits and are
set to a logic "0". The ISC Error field, IR[8:7], contains a "10"
when an ISC operation is a success; otherwise a "01" when
an In-System Configuration (ISC) operation fails. The
Erase/Program (ER/PROG) Error field, IR[6:5], contains a
"10" when an erase or program operation is a success; oth-
5
DS123 (v2.6) March 14, 2005
Preliminary Product Specification
XILINX [ XILINX, INC ]
