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7.5.10
Receive Slot Mask Registers (RSMA, RSMB)
Both receive slot mask registers are read/write registers. In Network mode, the receiver(s) use
these registers to determine which action to take in the current time slot. Depending on the
setting of the bits, the receiver(s) either tri-state the receiver(s) data signal(s) or receive a data
word and generate a receiver full condition.
23
22
21
11
10
9
RS11
RS10
RS9
—Reserved bit; read as 0; write to 0 0 for future compatibility.
Figure 7-16. ESSI Receive Slot Mask Register A (RSMA)
23
22
21
11
10
9
RS27
RS26
RS25
–Reserved. Read as zero. Write with zero for future compatibility.
Figure 7-17. ESSI Receive Slot Mask Register B (RSMB)
RSMA and RSMB (as in Figure 7-12 and Figure 7-13) can be seen as one 32-bit register,
RSM. Bit n in RSM (RSn) is an enable/disable control bit for time slot number N. When RSn
is cleared, all the data signals of the enabled receivers are tri-stated during time slot number
N. Data transfers from the receive data register(s) to the receive shift register(s), but the RDF
and ROE flags are not set. Consequently, during a disabled slot, no receiver full interrupt is
generated. The DSP is interrupted only for enabled slots. When RSn is set, the receive
sequence proceeds normally. Data is received during slot number N, and the RDF flag is set.
When the bits in the RSM are set, their setting affects the next frame transmission. The frame
being transmitted is not affected by the new RSM setting. If the RSM is read, it shows the
current setting.
When RSMA or RSMB is read by the internal data bus, the register contents occupy the two
low-order bytes of the data bus, and the high-order byte is filled by 0.
After a hardware
RESET
$FFFFFFFF, enabling all 32 time slots for data transmission.
20
19
18
8
7
6
RS8
RS7
RS6
(ESSI0 X:$FFFFB2, ESSI1 X:$FFFFA2)
20
19
18
8
7
6
RS24
RS23
RS22
(ESSI0 X:$FFFFB1, ESSI1 X:$FFFFA1)
signal or a software RESET instruction, the RSM register is reset to
Enhanced Synchronous Serial Interface (ESSI)
17
16
15
RS15
5
4
3
RS5
RS4
RS3
17
16
15
RS31
5
4
3
RS21
RS20
RS19
ESSI Programming Model
14
13
12
RS14
RS13
RS12
2
1
0
RS2
RS1
RS0
14
13
12
RS30
RS29
RS28
2
1
0
RS18
RS17
RS16
7-35
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