Z85233 Datasheet, PDF (27/317 Pages) Zilog, Inc. – The Zilog SCC Serial Communication Controller

SCC™/ESCC™ User’s Manual
Interfacing the SCC/ESCC
2.2 Z80X30 INTERFACE TIMING (Continued)
2.2.5 Z80C30 Register Enhancement
The Z80C30 has an enhancement to the NMOS Z8030
register set, which is the addition of a 10x19 SDLC Frame
Status FIFO. When WR15 bit D2=1, the SDLC Frame Sta-
tus FIFO is enabled, and it changes the functionality of
RR6 and RR7. See Section 4.4.3 for more details on this
feature.
2.2.6 Z80230 Register Enhancements
In addition to the Z80C30 enhancements, the 80230 has
several enhancements to the SCC register set. These in-
clude the addition of Write Register 7 Prime (WR7'), and
the ability to read registers that are read only in the 8030.
Write Register 7' is addressed by setting WR15 bit, D0=1
and then addressing WR7. Figure 2-4 shows the register
bit location of the six features enabled through this
register. All writes to address seven are to WR7' when
WR15, D0=1. Refer to Chapter 5 for detailed information
on WR7'.
WR7'
D7 D6 D5 D4 D3 D2 D1 D0
Auto Tx Flag
Auto EOM Reset
Auto RTS Turnoff
Rx FIFO Half Full
DTR/REQ Timing M
Tx FIFO Empty
External Read Enab
0
WR7' bit D6=1, enables the extended read register capa-
bility. This allows the user to read the contents of WR3,
WR4, WR5, WR7' and WR10 by reading RR9, RR4, RR5,
RR14 and RR11, respectively. When WR7' D6=0, these
write registers are write only.
Table 2-3 shows what functions are enabled for the various
combinations of register bit enables. See Table 2-1 (Shift
Left) and Table 2-2 (Shift Right) for the register address map
with the SDLC FIFO enabled only and the map with both the
extended read and SDLC FIFO features enabled.
Table 2-3. Z80230 SDLC/HDLC
Enhancement Options
WR15 WR7'
Bit D2 Bit D0 Bit D6 Functions Enabled
0
1
0 WR7' enabled only
0
1
1 WR7' with extended read
enabled
1
0
X 10x19 SDLC FIFO
enhancement
enabled only
1
1
0 10x19 SDLC FIFO and WR7'
1
1
1 10x19 SDLC FIFO and WR7'
with extended read enabled
Figure 2-4. Write Register 7 Prime (WR7')
2-8
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