zl50023 Zarlink Semiconductor, zl50023 Datasheet - Page 18

• Manufacturer Part Number: zl50023
• Description: Enhanced 4 K Channel Tdm Switch With Rate Conversion
• Manufacturer: Zarlink Semiconductor

4.1
There are 16 external high impedance control signals, STOHZ0 - 15, that are used to control the external drivers for
per-channel high impedance operations. Only the first sixteen ST-BUS/GCI-Bus (STio0 - 15) outputs are provided
with corresponding STOHZ signals. The STOHZ outputs deliver the appropriate number of control timeslot
channels based on the output stream data rate. Each control timeslot lasts for one channel time. When the ODE pin
is high and the OSB (bit 2) of the Control Register (CR) is also high, STOHZ0 - 15 are enabled. When the ODE pin,
OSB (bit 2) of the Control Register (CR) or the RESET pin is low, STOHZ0 - 15 are driven high, together with all the
ST-BUS/GCI-Bus outputs being tristated. Under normal operation, the corresponding STOHZ outputs of any
unused ST-BUS/GCI-Bus channel (high impedance) are driven high. Refer to Figure 16 on page 28 for a
diagrammatical explanation.
4.2
The frequency of the input clock (CKi) for the ZL50023 depends on the operation mode selected. In divided clock
mode, CKi must be at least twice the highest input or output data rate. For example, if the highest input data rate is
4.096 Mbps and the highest output data rate is 8.192 Mbps, the input clock, CKi, must be 16.384 MHz, which is
twice the highest overall data rate. The only exception to this is for 16.384 Mbps input or output data. In this case,
the input clock, CKi, is equal to the data rate. The input frame pulse, FPi, must always follow CKi. In multiplied clock
mode the frequency of CKi must be at least twice the highest input data rate regardless of the output data rate. An
APLL is used to multiple CKi to generate an internal clock that is used to output clocks and STio streams.
Following the example above, if the highest input data rate is 4.096 Mbps, the input clock, CKi, must be 8.192 MHz,
regardless of the output data rate. The only exception to this is for 16.384 Mbps input or output data. In this case,
the input clock, CKi, is equal to the data rate. The input frame pulse, FPi, must always follow CKi.
In either mode the user has to program the CKIN1 - 0 (bits 6 - 5) in the Control Register (CR) to indicate the width
of the input frame pulse and the frequency of the input clock supplied to the device.
The ZL50023 accepts positive and negative ST-BUS/GCI-Bus input clock and input frame pulse formats via the
programming of CKINP (bit 8) and FPINP (bit 7) in the Control Register (CR). By default, the device accepts the
negative input clock format and ST-BUS format frame pulses. However, the switch can also accept a positive-going
clock format by programming CKINP (bit 8) in the Control Register (CR). A GCI-Bus format frame pulse can be
used by programming FPINPOS (bit 9) and FPINP (bit 7) in the Control Register (CR).
8.192 Mbps or 16.384 Mbps
4.096 Mbps
2.048 Mbps
8.192 Mbps or 16.384 Mbps
4.096 Mbps
2.048 Mbps
Highest Input Data Rate
Highest Input or Output
External High Impedance Control, STOHZ0 -
Input Clock (CKi) and Input Frame Pulse (FPi) Timing
Data Rate
Table 2 - CKi and FPi Configurations for Multiplied Clock Mode
Table 1 - CKi and FPi Configurations for Divided Clock Modes
CKIN 1-0 Bits
CKIN 1-0 Bits
00
01
10
01
10
00
Zarlink Semiconductor Inc.
ZL50023
18
Input Clock Rate (CKi)
Input Clock Rate (CKi)
15
16.384 MHz
8.192 MHz
4.096 MHz
16.384 MHz
8.192 MHz
4.096 MHz
8 kHz (61 ns wide pulse)
8 kHz (122 ns wide pulse)
8 kHz (244 ns wide pulse)
Input Frame Pulse (FPi)
8 kHz (61 ns wide pulse)
8 kHz (122 ns wide pulse)
8 kHz (244 ns wide pulse)
Input Frame Pulse (FPi)
Data Sheet