
CYV15G0204RB
Document #: 38-02103 Rev. *C
Page 12 of 24
These pattern checkers are enabled by the associated
RXBISTx[1:0] latch via the device configuration interface.
When enabled, a register in the associated receive channel
becomes a signature pattern generator and checker by
logically converting to a Linear Feedback Shift Register
(LFSR). This LFSR generates a 511-character sequence. This
provides a predictable yet pseudo-random sequence that can
be matched to an identical LFSR in the attached Trans-
mitter(s). When synchronized with the received data stream,
the associated Receiver checks each character from the
deserializer with each character generated by the LFSR and
indicates compare errors and BIST status at the RXDx[1:0]
and BISTSTx bits of the Output Register.
The BIST status bus {BISTSTx, RXDx[0], RXDx[1]} indicates
010b or 100b for one character period per BIST loop to
indicate loop completion. This status can be used to check test
pattern progress.
The specific status reported by the BIST state machine is listed
in
Table 5
. These same codes are reported on the receive
status outputs.
If the number of invalid characters received ever exceeds the
number of valid characters by 16, the receive BIST state
machine aborts the compare operations and resets the LFSR
to look for the start of the BIST sequence again.
A device reset (RESET sampled LOW) presets the BIST
Enable Latches to disable BIST on both channels.
BIST Status State Machine
When a receive path is enabled to look for and compare the
received data stream with the BIST pattern, the {BISTSTx,
RXDx[0], RXDx[1]} bits identify the present state of the BIST
compare operation.
The BIST state machine has multiple states, as shown in
Figure 2
and
Table 5
. When the receive PLL detects an
out-of-lock condition, the BIST state is forced to the
Start-of-BIST state, regardless of the present state of the BIST
state machine. If the number of detected errors ever exceeds
the number of valid matches by greater than 16, the state
machine is forced to the WAIT_FOR_BIST state where it
monitors the receive path for the first character of the next
BIST sequence.
Power Control
The CYV15G0204RB supports user control of the powered up
or down state of each transmit and receive channel. The
receive channels are controlled by the RXPLLPDx latch via the
device configuration interface. When RXPLLPDx = 0, the
associated PLL and analog circuitry of the channel is disabled.
The transmit channels are controlled by the OE1x and the
OE2x latches via the device configuration interface. The
reclocker function is controlled by the ROE1x and the ROE2x
latches via the device configuration interface. When a driver is
disabled via the configuration interface, it is internally powered
down to reduce device power. If both serial drivers for a
channel are in this disabled state, the associated internal logic
for that channel is also powered down. When the reclocker
serial drivers are disabled, the reclocker function will be
disabled, but the deserialization logic and parallel outputs will
remain enabled.
Device Reset State
When the CYV15G0204RB is reset by assertion of RESET, all
state machines, counters, and configuration latches in the
device are initialized to a reset state. Additionally, the JTAG
controller must also be reset for valid operation (even if JTAG
testing is not performed). See
“JTAG Support” on page 14
for
JTAG state machine initialization. See
Table 3 on page 13
for
the initialize values of the configuration latches.
Following a device reset, it is necessary to enable the receive
channels used for normal operation. This can be done by
sequencing the appropriate values on the device configuration
interface.
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Device Configuration and Control Interface
The CYV15G0204RB is highly configurable via the configu-
ration interface. The configuration interface allows each
channel to be configured independently.
Table 3 on page 13
lists the configuration latches within the device including the
initialization value of the latches upon the assertion of RESET.
Table 4 on page 14
shows how the latches are mapped in the
device. Each row in the
Table 4
maps to a 7-bit latch bank.
There are 6 such write-only latch banks. When WREN = 0, the
logic value in the DATA[6:0] is latched to the latch bank
specified by the values in ADDR[2:0]. The second column of
Table 4
specifies the channels associated with the corre-
sponding latch bank. For example, the first three latch banks
(0,1 and 2) consist of configuration bits for channel A.
Latch Types
There are two types of latch banks: static (S) and dynamic (D).
Each channel is configured by 2 static and 1 dynamic latch
banks. The S type contain those settings that normally do not
change for a given application, whereas the D type controls
the settings that could change during the application's lifetime.
The first and second rows of each channel (address numbers
0, 1, 5, and 6) are the static control latches. The third row of
latches for each channel (address numbers 2, 7) are the
dynamic control latches that are associated with enabling
dynamic functions within the device. Address numbers 3 and
4 are internal test registers.
Static Latch Values
There are some latches in the table that have a static value (ie.
1, 0, or X). The latches that have a ‘1’ or ‘0’ must be configured
with their corresponding value each time that their associated
latch bank is configured. The latches that have an ‘X’ are don’t
cares and can be configured with any value.
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