
13-12
Lattice Semiconductor
LatticeXP sysCONFIG Usage Guide
while the other Lattice FPGA devices in the daisy chain operate in Slave Serial mode. The RESET/OE pin of the
PROM is driven by INITN while the Chip Select pin is driven by the DONE pin of the devices.
Figure 13-4. Master and Slave Serial Daisy Chain
Slave Parallel Mode
In Slave Parallel mode a host system sends the configuration data in a byte-wide stream to the device. The CCLK,
CSN, CS1N, and WRITEN pins are driven by the host system. The Slave Parallel configuration mode allows multi-
ple devices to be chained in parallel, as shown in
Figure 13-5.WRITEN, CSN, and CS1N must be held low to write to the device; data is input from D[0:7]. Slave Parallel mode
can also be used for readback of the internal configuration. By driving the WRITEN pin low, and CSN and CS1N
low, the device will input the readback instructions on the D[0:7] pins; WRITEN is then driven high and data read on
D[0:7]. In order to support readback the PERSISTENT bit in ispLEVER’s Preference Editor must be set to ON.
The Slave Parallel mode can support two types of overflow, Bypass and Flow-Through. If the Bypass option is set,
after the first device has received all of its configuration data, the data presented to the D[0:7] pins will be serialized
and bypassed to the DOUT pin. If the Flow-Through option is set, after the first device has received all of its config-
uration data, the CSON signal will drive the following parallel mode device’s chip select low as shown in
Figure 13-To support asynchronous configuration, where the host may provide data faster than the FPGA can accept it, Slave
Parallel mode can use the BUSY signal. By driving the BUSY signal high the Slave Parallel device tells the host to
Configuration Mode
CFG[1]
CFG[0]
CONFIG_MODE
Chain Mode
Slave Parallel (no overload option)
1
0
Slave_Parallel
Disable
Slave Parallel (Bypass ON)
1
0
Slave_Parallel
Bypass
Slave Parallel (Flow Through ON)
1
0
Slave_Parallel
Flowthrough
LatticeXP
Master Serial
CCLK
PROGRAMN
INITN
DONE
DIN
DOUT
CFG0
CFG1
LatticeXP
Slave Serial
CCLK
PROGRAMN
INITN
DONE
DIN
CFG1
CFG0
Master Program
Serial
PROM
DATA
CLK
RESET/OE
CS