2.0 Circuit Description
CX28394/28395/28398
2.5 Microprocessor Interface
Quad/x16/Octal—T1/E1/J1 Framers
2.5.4 Device Reset
The device contains four reset methods:
1. Internal Power-On Reset (POR),
2. Hardware Reset which uses the RST* pin,
3. Global Software Reset which uses the GRESET bit in register FCR [addr
080], and
4. Software Reset which uses the RESET bit in register CR0 [addr 001].
All four methods result in device outputs placed in a high-impedance state and
configuration registers set to default values as shown in Table 3-4, Address Map.
In all reset methods, SYSCKI must be present during the reset process for proper
operation. MCLK (internal or external) performs the actual register initialization.
Therefore, if the SYNCMD pin is connected high to enable external MCLK, the
external MCLK must be applied during reset, and if the SYNCMD pin is low
during reset, the internal clock (33 MHz) is used and external MCLK is not
required. After hardware reset, software reset, or internal power-on reset, the
microprocessor must initialize the configuration registers to the desired state.
An internal POR process is initiated during power-up. When VDD has
reached approximately 2.0 V, the internal reset process begins and continues for
100 SYSCKI cycles if SYSCKI is applied. If SYSCKI is not present, the device
remains in the reset state and does not terminate until detecting 100 SYSCKI
cycles. GRESET or RESET can be monitored to determine when POR is
complete. MCLK (internal or external) must be present during the POR
concurrent with SYSCKI to allow register initialization.
Hardware reset is initiated by bringing the RST* pin active (low) for a
minimum of 4 µs. If SYNCMD is high (using external MCLK), external MCLK
must be present while RST* is low to allow register initialization. After RST* is
deactivated, the internal reset process continues for 5 µs and register access
should be avoided. GRESET can be monitored to determine when the reset
process is complete.
2-58
Conexant
100054E
CONEXANT [ CONEXANT SYSTEMS, INC ]
