
2-7
2—SOFTWARE
ISD-SR3000
ISD
MWRQST
MICROWIRE Request. When active (0), this signal indicates that new status information is
available. MWRQST is deactivated (set to 1), after the ISD-SR3000 receives a GSW (Get Sta-
tus Word) command from the host controller. After reset, this signal becomes active (0) to indi-
cate that a reset occurred. MWRQST, unlike all the signals of the communication protocol, is
an asynchronous line that is controlled by the ISD-SR3000 firmware.
2.5.3
After reset, both MWRQST and MWRDY are cleared to 0.
SIGNAL USE IN THE INTERFACE PROTOCOL
The MWRQST signal is activated to indicate that a reset occurred. The EV_RESET bit in the
status register is used to indicate a reset condition.
The GSW command should be issued after reset to verify that the EV_RESET event occurred,
and to deactivate the MWRQST signal.
While the MWCS signal is active (0), the ISD-SR3000 reads data from MWDIN on every rising
edge of MWCLK. The ISD-SR3000 also writes every bit back to MWDOUT. This bit is either the
same bit, which was read from MWDIN (in this case it is written back as a synchronization echo
after some propagation delay), or it is a bit of a value the ISD-SR3000 transmits to the host con-
troller (in this case it is written on every falling edge of the clock).
When a command has more than one parameter/return-value, the parameters/return-values
are transmitted in the order of appearance. If a parameter/return-value is more than one byte
long, the bytes are transmitted from the most significant to the least significant.
The MWRDY signal is used as follows:
1.
Active (0) MWRDY signals the host controller that the last eight bits of data transferred
to/from the voice module were accepted and processed (see below).
2.
The MWRDY signal is deactivated (set to 1 by the ISD-SR3000) after 8-bits of data were
transferred to/from the ISD-SR3000. The bit is set following the falling edge of the eighth
MWCLK clock-cycle.
3.
The MWRDY signal is activated (cleared to 0) by the ISD-SR3000 when it is ready to re-
ceive the first parameter byte (if there are any parameters) and so on until the last byte
of parameters is transferred. An active MWRDY signal after the last byte of parameters
indicates that the command was parsed and (if possible) executed. If that command has
a return value, the host controller must read the value before issuing a new command.
4.
When a return value is transmitted, the MWRDY signal is deactivated after every byte,
and activated again when the ISD-SR3000 is ready to send another byte or receive a new
command.
The MWRDY signal is activated (cleared to 0) after reset, and after a protocol time-out.
The MWRQST signal is used as follows: