RS8953 Conexant Systems, Inc., RS8953 Datasheet - Page 113

• Manufacturer Part Number: RS8953
• Description: High-bit-rate Digital Subscriber Line (hdsl) Channel unit
• Manufacturer: Conexant Systems, Inc.

RS8953B/8953SPB
HDSL Channel Unit
TCLK_SEL
RCLK_SEL
PP_LOOP
HP_LOOP
PCM_FLOAT
GCLK_SEL
N8953BDSB
0xE6—Command Register 2 (CMD_2)
GCLK_SEL
7
PCM_FLOAT
PCM Transmit Clock Source—Selects which clock source and clock edge are used for PCM
transmit inputs and outputs.
PCM Receive Clock Source—Selects which clock source and which clock edge is used for
PCM receive outputs. See also RCLK_INV [CMD_7; addr 0xF4].
NOTE:
Loopback Towards PCM on the PCM Side—The RSER and RMSYNC outputs are connected
from TSER and TMSYNC inputs. Signals are switched directly at the I/O pins, without
switching the PCM receive clock. The MPU must change RCLK_SEL to source RCLK from
the TCLK input. HDSL transmit and receive channels operate normally, except the receive
channel outputs are replaced by loopback signals.
Loopback Towards HDSL on the PCM Side—The TSER and TMSYNC inputs are replaced by
data and multiframe sync generated from the PCM receive formatter, without switching the
PCM transmit clock. The MPU must change TCLK_SEL to source TCLK from the RCLK
output. The PCM receiver operates normally, but the transmit TSER and TMSYNC inputs are
ignored.
NOTE:
Float PCM Multiframes—Selects whether MSYNC accepts TMSYNC as a frame and/or
multiframe sync reference. MSYNC is always used to establish transmit frame and multiframe
alignment for PCM and HDSL frames. If PCM_FLOAT is active, MSYNC ignores TMSYNC
and allows unframed or asynchronous payload mapping of PCM frames into HDSL frames. In
this case, TFRAME_LOC and TMF_LOC [addr 0xC0–0xC2] are also ignored. When
PCM_FLOAT is zero, the TMSYNC input acts as the frame and/or multiframe sync reference
for MSYNC.
General Purpose Clock Source—Synchronizes MPU bus cycles and quantizes DPLL phase
error.
6
TCLK_SEL = 1x and RCLK_SEL = 11; both must not be set simultaneously.
PP_LOOP and HP_LOOP cannot be activated simultaneously.
HP_LOOP
5
0 = Normal PCM receive
1 = RSER and RMSYNC supplied by PCM transmit inputs
0 = Normal PCM transmit operation
1 = Transmit PCM data supplied by PCM receiver channel
0 = MSYNC accepts TMSYNC as transmit sync reference
1 = MSYNC ignores TMSYNC
0 = GCLK supplied by HFCLK
1 = GCLK supplied by TCK pin
00
01
1x
00
01
10
11
PP_LOOP
TCLK (rising edge outputs, falling edge inputs)
TCLK inverted (falling edge outputs, rising edge inputs)
PCM receive clock source (see RCLK_SEL)
DPLL recovered clock (rising edge outputs)
EXCLK pin (rising edge outputs)
EXCLK pin inverted (falling edge outputs)
PCM transmit clock source (see TCLK_SEL)
4
Conexant
3
RCLK_SEL[1:0]
PLL_DIV
2
4.11 Common Command
1
TCLK_SEL[1:0]
4.0 Registers
0
4-45