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7.5.7 ESSI Transmit Data Registers (TX[2–0])
ESSI0:TX20, TX10, TX00; ESSI1:TX21, TX11, TX01
TX2, TX1, and TX0 are 24-bit write-only registers. Data written into these registers
automatically transfers to the transmit shift registers. (See Figure 7-12 and Figure 7-13.) The
data transmitted (8, 12, 16, or 24 bits) is aligned according to the value of the ALC bit. When the
ALC bit is cleared, the MSB is Bit 23. When ALC is set, the MSB is Bit 15. If the transmit data
register empty interrupt has been enabled, the DSP is interrupted whenever a transmit data
register becomes empty.
Note:
When data is written to a peripheral device, there is a two-cycle pipeline delay while
any status bits affected by this operation are updated. If any of those status bits are read
during the two-cycle delay, the status bit may not reflect the current status.
7.5.8 ESSI Time Slot Register (TSR)
TSR is effectively a write-only null data register that prevents data transmission in the current
transmit time slot. For timing purposes, TSR is a write-only register that behaves as an alternative
transmit data register, except that, rather than transmitting data, the transmit data signals of all the
enabled transmitters are in the high-impedance state for the current time slot.
7.5.9 Transmit Slot Mask Registers (TSMA, TSMB)
Both transmit slot mask registers are read/write registers. When the TSMA or TSMB is read to
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. In Network mode the transmitter(s) use these registers to determine
which action to take in the current transmission slot. Depending on the bit settings, the
transmitter(s) either tri-state the transmitter(s) data signal(s) or transmit a data word and generate
a transmitter empty condition.
23
22
21
11
10
9
TS11
TS10
TS9
—Reserved bit; read as 0; write to 0 0 for future compatibility.
Figure 7-14. ESSI Transmit Slot Mask Register A (TSMA)
Freescale Semiconductor
20
19
18
8
7
6
TS8
TS7
TS6
(ESSI0 X:$FFFFB4, ESSI1 X:$FFFFA4)
DSP56311 User's Manual, Rev. 2
15
17
16
TS15
5
4
3
TS5
TS4
TS3
ESSI Programming Model
14
13
12
TS14
TS13
TS12
2
1
0
TS2
TS1
TS0
7-31
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