Freescale Semiconductor, Inc.
Motorola Interconnect Bus (MI BUS)
SCI/MI BUS2 registers
6.10.2 S2BDH, S2BDL — MI BUS clock rate control registers
State
on reset
S2B12 S2B11 S2B10 S2B9 S2B8 0000 0000
Address bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
SCI/MI 2/3 baud high (S2BDH) $0050 B2TST B2SPL
0
SCI/MI 2/3 baud low (S2BDL) $0051 S2B7 S2B6 S2B5 S2B4 S2B3 S2B2 S2B1 S2B0 0000 0100
The contents of this register determine the clock rate for both MI BUS 2
and MI BUS 3.
S2B[12:0] — SCI baud rate/ MI BUS clock rate selects
Use the following formula to calculate MI BUS 2/3 clock rate. Refer to
the table of baud rate control values (Table 5-1) for example rates:
ST4XCK
MI BUS clock rate = ----------------------------
16 × (2BR)
where the baud rate control value (BR) is the contents of S2BDH/L
(BR = 1, 2, 3,... 8191).
BR = 0 disables the clock rate generator.
6.10.3 S2CR1 — MI BUS2 control register 1
State
Address bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
on reset
SCI/MI 2 control 1 (S2CR1)
$0052 LOPS2WOMS2 MIE2 M2 WAKE2 ILT2 PE2
PT2 0000 0000
WOMS2 — Wired-OR mode for MI BUS2 pins (PH4, PH5)
1 = TXD2 and RXD2 are open drains if operating as outputs.
0 = TXD2 and RXD2 operate normally.
MIE2 — Motorola interface bus enable 2
1 = MI BUS is enabled for this subsystem.
0 = The SCI functions normally.
When MIE2 is set, the SCI2 registers, bits and pins assume the
functionality required for MI BUS.
PT2 — MI BUS TX polarity
1 = MI BUS transmit pin will send inverted data.
0 = MI BUS transmit pin functions normally.
MC68HC11P2 — Rev 1.0
Technical Data
Motorola Interconnect Bus (MI BUS)
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