36
Agere Systems Inc.
Preliminary Data Sheet
September 2001
T8535B/T8536B Quad Programmable Codec
Timing Characteristics
(continued)
PCM Interface Timing
Single-Clocking Mode
Frame sync (FS) signifies the start of frame on the
PCM bus for all four channels. FS occurs every 125
μ
s
at an 8 kHz rate. FS must be synchronous with the
PCM bus clock (BCLK) and must be high for a mini-
mum of one BCLK period. The PCM interface operates
using fixed data rate timing, data timing for both trans-
mit and receive are controlled by BCLK. BCLK can
be any value from 512 kHz (eight time slots) to
16.384 MHz (256 time slots) as defined by Table 18.
The PCM bus transfers the most significant bit of the
time slot first, consistent with normal telephony prac-
tice. Figure 24 shows FS, DX, and DR beginning on the
rising edge of BCLK and being latched on the falling
edge of BCLK. Figure 25 shows DX and DR beginning,
and FS being latched on the rising edge of BCLK, and
DX and DR being latched on the falling edge of BCLK.
Figure 24 portrays a bit offset of zero, and Figure 25
portrays a transmit bit offset of one and a receive bit
offset of two. Bit offset skews the PCM transmit and/or
receive data independently from the FS reference. Up
to seven BCLK cycles of bit offset can be employed on
a per-channel basis. This flexibility can accommodate
special timing requirements.
Linear coding is transmitted and received in two con-
secutive 8-bit time slots. TSX0 or TSX1 is active (low)
when DX data is transmitting (8 bits for companded
code, 16 bits for linear code).
Table 18.
PCM Interface
Timing: Single-Clocking Mode
(See Figures 24 and 25.)
Symbol
f
BCLK
Parameter
Test Conditions
—
—
—
—
—
—
—
—
—
Min
—
—
—
—
—
—
—
—
—
Typ
512
1024
1536
2048
3072
4096
8192
16384
—
Max
—
—
—
—
—
—
—
—
Unit
kHz
kHz
kHz
kHz
kHz
kHz
kHz
kHz
—
Allowable BCLK Frequencies
—
Jitter of BCLK
100 ns in
100 ms =
1 ppm
60
—
—
125
μ
s
t
BCLK
—
BCLK Duty Cycle
Frame Strobe Setup Time
Frame Strobe Hold Time
Frame Strobe Width
—
40
7
4
t
BCLK
50
—
—
—
%
ns
ns
—
t
FSSETUP
t
FSHOLD
t
FSWIDTH
B
CLK
= 16.384 MHz
B
CLK
= 16.384 MHz
FS synchronous with
BCLK
B
CLK
= 16.384 MHz
B
CLK
= 16.384 MHz
B
CLK
= 16.384 MHz
B
CLK
= 16.384 MHz
B
CLK
= 16.384 MHz
I
L
= 15 mA,
C
LOAD
= 100 pF
C
LOAD
= 0
—
—
t
XDLY
t
IDHOLD
t
IDSETUP
t
RISE
t
FALL
t
RISE
,
t
FALL
t
DXHIGHZ
t
TSXDELAY
Line Driver Enable Delay
t
TSXHIGHZ
Line Driver Enable Float on TS Exit
Output Data Delay
Input Data Hold Time
Input Data Setup Time
Clock Edge Rise Time
Clock Edge Fall Time
DX Output Rise/Fall Time
—
4
7
—
—
—
—
—
—
—
—
—
9
—
—
8
8
30
ns
ns
ns
ns
ns
ns
DX Output Data Float on TS Exit
—
—
—
—
—
—
5
5
5
ns
ns
ns