W681513 Datasheet, PDF (11/33 Pages) Winbond – 5V SINGLE-CHANNEL VOICEBAND CODEC FOR USB APPLICATIONS

W681513
become low impedance when the Frame Sync signal FST is high or when the 8 bit data word is being
transmitted. The transmit data pin PCMT will become high impedance when the Frame Sync signal
FST becomes low while the data is transmitted or when half of the LSB is transmitted. The internal
decision logic will determine whether the next frame sync is a long or a short frame sync, based on the
previous frame sync pulse. To avoid bus collisions, the PCMT pin will be high impedance for two
frame sync cycles after every power down state. More detailed timing information can be found in the
interface timing section.
7.4.2. Short Frame Sync
The W681513 operates in the Short Frame Sync Mode when the Frame Sync signal at pin FST is high
for one and only one falling edge of the bit-clock at the BCLKT pin. On the following rising edge of the
bit-clock, the W681513 starts clocking out the data on the PCMT pin, which will also change from high
to low impedance state. The data transmit pin PCMT will go back to the high impedance state halfway
the LSB. The Short Frame Sync operation of the W681513 is based on an 8-bit data word. When
receiving data on the PCMR pin, the data is clocked in on the first falling edge after the falling edge
that coincides with the Frame Sync signal. The internal decision logic will determine whether the next
frame sync is a long or a short frame sync, based on the previous frame sync pulse. To avoid bus
collisions, the PCMT pin will be high impedance for two frame sync cycles after every power down
state. More detailed timing information can be found in the interface timing section.
7.4.3. General Circuit Interface (GCI)
The GCI interface mode is selected when the BCLKR pin is connected to V_SS for two or more frame
sync cycles. It can be used as a 2B+D timing interface in an ISDN application. The GCI interface
consists of 4 pins : FSC (FST), DCL (BCLKT), Dout (PCMT) & Din (PCMR). The FSR pin selects
channel B1 or B2 for transmit and receive. Data transitions occur on the positive edges of the data
clock DCL. The Frame Sync positive edge is aligned with the positive edge of the data clock DCLK.
The data rate is running half the speed of the bit-clock. The channels B1 and B2 are transmitted
consecutively. Therefore, channel B1 is transmitted on the first 16 clock cycles of DCL and B2 is
transmitted on the second 16 clock cycles of DCL. For more timing information, see the timing section.
- 11 -
Publication Release Date: October 1, 2003
Revision A3