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AN93
120 Rev. 1.3
5.7.21. U87 (Synchronous Access Mode Configuration Register)
U87 SAM Synchronous Access Mode Configuration Options
Bit Name Function
15:11 Reserved Read returns zero.
10 MINT Minimal Transparency
Host software must always set this bit.
0 = Generate two-byte <EM> transparency sequences. This option will use codes
<EM><T5> through <RM><T20> (if possible) for received data containing two back-to-
back bytes requiring transparency (Rev C and later).
1 = Generate one-byte <EM>transparency sequences. This option will only use codes
<EM><T1> through <EM><T4> for received data (Rev B and later).
9 SERM Special Error Reporting Mode
0 = Ignore unrecognized in-band commands.
1 = Generate <EM><0x45> (“E” for error) in response to any unrecognized in-band
commands.
8FSMSFramed Sub-Mode Startup
0 = Upon successful connection, enter Transparent Sub-Mode. An <EM><FLAG>
is required to enter Framed Sub-Mode.
1 = Upon successful connection, immediately enter Framed Sub-Mode. The first
received <EM><err> (from a successful hunt) is transformed into an <EM><flag>.
7:0 XMTT Transmitter Threshold
This value represents the number of bytes before a transmission is started. The follow-
ing values are special:
0 The same as ten. Upon receipt of ten bytes, data are transferred. The DTE must
supply a closing flag within the required time or an underrun will occur.
255 The same as infinity, e.g. never start a packet until the closing flag is received.