Receive Slot Mask Registers (Rsma, Rsmb) - Motorola DSP56305 User Manual

Enhanced Synchronous Serial Interface (ESSI)
ESSI Programming Model
transferred from the enabled Transmit Data Register(s) to the Transmit Shift Register.
However, the TDE and the TUE flags are not set. This means that during a disabled slot,
no transmitter empty interrupt is generated. The DSP is interrupted only for enabled
slots. Data written to the Transmit Data Register when servicing the transmitter empty
interrupt request is transmitted in the next enabled transmit time slot.
When TSMk is set, the transmit sequence proceeds normally. Data is transferred from
the TX register to the Shift Register during slot number K and the TDE flag is set.
Changing the bits in the TSM affects the next frame transmission. The frame currently
being transmitted is not affected by the new TSM value. If the TSM is read, it shows the
current value.
Using the TSM slot mask does not conflict with using the TSR. Even if a slot is enabled in
the TSM, the user may choose to write to the TSR to tri-state the transmit data signals of
the enabled transmitters during the next transmission slot.
After a hardware or software reset instruction, the TSM register is reset to $FFFFFFFF,
which enables all thirty-two slots for data transmission.
7.4.10

Receive Slot Mask Registers (RSMA, RSMB)

The Receive Slot Mask Registers are two 16-bit read/write registers. In Network mode,
these registers are used by the receiver(s) to determine what action to take in the current
time slot. Depending on the setting of the bits, the receiver(s) either tri-state their data
signal(s) or receive a data word and generate a receiver full condition (RDF = 1).
RSMA and RSMB (see Figure 7-19 and Figure 7-20) can be seen as one 32-bit register,
RSM. Bit k in RSM (RSMk) is an enable/disable control bit for time slot number K. When
RSMk is cleared, all the data signals of the enabled receivers are tri-stated during time
slot number K. Data is not transferred from the Receive Data Register(s) to the Receive
Shift Register(s) and the RDF and ROE flags are not set. During a disabled slot, no
receiver full interrupt is generated. The DSP is interrupted only for enabled slots.
When RSMk is set, the receive sequence proceeds normally. Data shifted into the Receive
Shift Register is transferred into the Receive Data Register during slot number K, and the
RDF flag is set.
Changing the bits in the RSM affects the next frame transmission. The frame currently
being received is not affected by the new RSM value. If the RSM is read, it shows the
current value.
MOTOROLA DSP56305 User's Manual 7-41