PRELIMINARY
CYP15G0401RB
Document #: 38-02111 Rev. ** Page 16 of 35
.
When the Cypress or Alternate Mode Framer is enabled and
half-rate receive port clocking is also enabled
(RFMODE
≠
LOW and RXRATE = HIGH), the output clock is
not modified when framing is detected, but a single pipeline
stage may be added or subtracted from the data stream by the
Framer logic such that the rising edge of RXCLKx+ occurs
when COMDETx is present on the associated output bus.
This adjustment only occurs when the Framer is enabled
(RFEN = HIGH). When the Framer is disabled, the clock
boundaries are not adjusted, and COMDETx may be asserted
during the rising edge of RXCLK– (if an odd number of
characters were received following the initial framing).
Parity Generation
In addition to the eleven data and status bits that are presented
by each channel, an RXOPx parity output is also available on
each channel. This allows the CYP15G0401RB to support
ODD parity generation for each channel. To handle a wide
range of system environments, the CYP15G0401RB supports
different forms of parity generation, including no parity.
When the decoders are enabled (DECMODE
≠
LOW), parity
can be generated on
• the RXDx[7:0] character
• the RXDx[7:0] character and RXSTx[2:0] status.
When the decoders are bypassed (DECMODE = LOW), parity
can be generated on
• the RXDx[7:0] and RXSTx[1:0] bits
• the RXDx[7:0] and RXSTx[2:0] bits.
These modes differ in the number of bits which are included in
the parity calculation. Only ODD parity is provided which
ensures that at least one bit of the data bus is always a logic-1.
Those bits covered by parity generation are listed in
Table 8
.
Parity generation is enabled through the three-level select
PARCTL input. When PARCTL = LOW, parity checking is
disabled, and the RXOPx outputs are all disabled (High-Z).
When PARCTL = MID (open) and the decoders are enabled
(DECMODE
≠
LOW), ODD parity is generated for the received
and decoded character in the RXDx[7:0] signals and is
presented on the associated RXOPx output. When
PARCTL = MID and the decoders are bypassed
(DECMODE = LOW), ODD parity is generated for the received
and decoded character in the RXDx[7:0] and RXSTx[1:0] bit
positions. When PARCTL = HIGH, ODD parity is generated for
the RXDx[7:0] and the associated RXSTx[2:0] status bits.
Receive Status Bits
When the 10B/8B Decoder is enabled (DECMODE
≠
LOW),
each character presented at the Output Register includes
three associated status bits. These bits are used to identify:
• if the contents of the data bus are valid
• the type of character present
• the state of receive BIST operations (regardless of the state
of DECMODE)
• character violations.
These conditions normally overlap; e.g., a valid data character
received with incorrect running disparity is not reported as a
valid data character. It is instead reported as a Decoder
violation of some specific type. This implies a hierarchy or
priority level to the various status bit combinations. The
hierarchy and value of each status is listed in
Table 9
.
The receive status when normal data is received is shown in
Table 9
. The receive status when Receive BIST is enabled is
shown in
Table 10
.
Notes:
10.Receive path parity output drivers (RXOPx) are disabled (High-Z) when PARCTL = LOW.
11. When the Decoder is bypassed (DECMODE = LOW) and BIST is not enabled (Receive BIST Latch output is HIGH), RXSTx[2] is driven to a logic-0, except when
the character in the output buffer is a framing character.
Table 7. Decoder Bypass Mode (DECMODE = LOW)
Signal Name Bus Weight 10Bit Name
RXSTx[2]
(LSB)
COMDETx
RXSTx[1] 2
0
a
RXSTx[0] 2
1
b
RXDx[0] 2
2
c
RXDx[1] 2
3
d
RXDx[2] 2
4
e
RXDx[3] 2
5
i
RXDx[4] 2
6
f
RXDx[5] 2
7
g
RXDx[6] 2
8
h
RXDx[7]
(MSB)
2
9
j
Table 8. Output Register Parity Generation
Signal
Name
Receive Parity Generate Mode (PARCTL)
LOW
[10]
MID
HIGH
DECMODE
= LOW
DECMODE
≠ LOW
RXSTx[2] X
[11]
RXSTx[1] X X
RXSTx[0] X X
RXDx[0] X X X
RXDx[1] X X X
RXDx[2] X X X
RXDx[3] X X X
RXDx[4] X X X
RXDx[5] X X X
RXDx[6] X X X
RXDx[7] X X X
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