xcr3320 Xilinx Corp., xcr3320 Datasheet - Page 24

• Manufacturer Part Number: xcr3320
• Description: Xcr3320 320 Macrocell Sram Cpld
• Manufacturer: Xilinx Corp.

Daisy Chain Operation
Multiple XCR3320s can be configured by using a
daisy-chain of XCR3320s. Daisy-chaining uses a lead
XCR3320 and one or more XCR3320s configured in slave
serial mode. The lead XCR3320 can be configured in any
mode.
ple XCR3320s in a daisy-chain configuration with the lead
devices configured in master parallel mode.
shows the connections for loading multiple XCR3320’s with
the lead device configured in master serial mode.
Daisy-chained XCR3320s are connected in series. An
upstream XCR3320 which has received the preamble out-
puts a high on dout, ensuring that downstream XCR3320s
do not receive frame start bits. When the lead device
receives the postamble, its configuration is complete. At
this point, the configuration RAM of the lead device is full
and its done pin is released. The lead device continues to
load configuration data until the internal frame bit counter
reaches the length count or all the done pins of the chain
have gone high. Since the configuration RAM of the lead
device is full, this data is shifted out serially to the down-
stream devices on the dout pin. As the configuration is
completed for the downstream devices, each will release
its done pin. Because the done pins of each device in the
chain are wire-anded together, the done pin will be pulled
DS033 (v1.3) October 9, 2000
Figure 27: Daisy-Chain Schematic with Lead Device in Master Parallel
PROGRAM
EEPROM
Figure 27
A[19:0]
D[7:0]
OE
CE
R
shows the connections for loading multi-
This product has been discontinued. Please see
V
CC
D[7:0]
cclk
A[19:0]
done
prgmn
M3
M2
M1
M0
PARALLEL/LEAD
MASTER
crcerrn
dout
ldcn
hdc
Figure 28
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V
CC
cclk
din
done
prgmn
M3
M2
M1
M0
high when all devices in the daisy-chain have completed
configuration. All devices now move to the start-up state
simultaneously.
The generation of cclk for the daisy-chained devices which
are in slave serial mode differs depending on the configura-
tion mode of the lead device. A master parallel mode
device uses its internal timing generator to produce an
internal cclk. If the lead device is configured in either syn-
chronous peripheral, slave serial mode, or slave parallel
mode, cclk is an input and is mated to the lead device and
to all of the daisy-chained devices in parallel. The configu-
ration data is read into din of slave devices on the positive
edge of cclk, and shifted out dout on the negative edge of
cclk. Note that daisy-chain operation is limited to a cclk fre-
quency of 1 MHz. If a CRC error or an invalid preamble is
detected by a slave device, crcerrn will be pulled low and in
turn pull prgmn low, halting configuration for all devices. If a
CRC error is detected by the master device, hdc will be
pulled low, resetting the EEPROM to the first address and
restarting configuration.
The development software can create a composite config-
uration file for configuring daisy-chained XCR3320s. The
configuration data consists of multiple concatenated data
packets.
SLAVE #1
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XCR3320: 320 Macrocell SRAM CPLD
crcerrn
dout
ldcn
hdc
V
CC
cclk
din
done
prgmn
M3
M2
M1
M0
SLAVE #2
crcerrn
dout
ldcn
hdc
SP00670
for details.
V
V
CC
CC
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