Receive Slot Mask Shift Register - Rsms; Ssi Operating Modes - Motorola DSP56156 Manual

The 32-bit mask which is written into RSMx, is transferred to the Receive Slot Mask Shift
Register (RSMS) during the last slot of the last frame. Writing to RSMx will not affect the
state of the active (enabled) receive slots during the current receive frame, but only that
of the next frame.
After DSP reset, the Receive Slot Mask Register is preset to $FFFFFFFF, which means
that all 32 possible slots are enabled for data reception.
Note: The Receive Slot Mask Registers have to be written before the last three serial
clock cycles of a frame in order to become active at the beginning of the next frame.
8.18

RECEIVE SLOT MASK SHIFT REGISTER - RSMS

The Receive Slot Mask Shift Register (RSMS) is a 32-bit shift register. At the beginning
of each receive frame, it is loaded with the 32-bit mask from RSM. Then, it is shifted one
bit to the right near the end of each received word. The LSB of RSMSR is used as an en-
able/disable for receiving a word and setting the RDF flag. This register is not accessible
to the programmer.
8.19

SSI OPERATING MODES

The SSI on-chip peripheral can operate in three operating modes – Normal, Network, and
On-Demand. In the Normal and Network modes, data is transferred and interrupts are
generated (if enabled) periodically. The On-Demand mode is a special mode which per-
mits data to be transferred serially when necessary in a non-periodic fashion.
8 - 24 SYNCHRONOUS SERIAL INTERFACE (SSI0 and SSI1)
RECEIVE SLOT MASK SHIFT REGISTER - RSMS
Table 8-5 SSI modes
Mode SYN
Normal Async
Sync
Network Async
Sync
On-Demand Async
Sync
SC1x SC0x
RFS In TFS In
RFS Out TFS Out
RFS In TFS Out
— FS In
— FS Out
RFS In TFS In
RFS Out TFS Out
RFS In TFS Out
— FS In
— FS Out
RFS Out TFS Out
RFS In TFS Out
— FS Out
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