P8044AH-R0117 datasheet(37/65 Pages) INNOVASIC

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IA8044/IA8344

Data Sheet

SDLC Communications Controller

March 30, 2010

IA211010112-04

http://www.Innovasic.com

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three serial data link configurations, 1) half-duplex, point-to-point, 2) half-duplex, multipoint,

or 3) loop mode.

4.10.1 SIU Special Function Registers

The CPU controls the SIU and receives status from the SIU via 11 SFRs. The Serial Interface

Unit Control Registers are detailed in the sections that follow.

4.10.2 Serial Mode Register (SMD)

Table 31 presents the serial mode register, which sets the operational mode of the SIU. The CPU

can read and write SMD. The SIU can read SMD. To prevent conflicts between CPU and SIU,

accesses to SMD the CPU should write SMD only when RTS and RBE bits in the STS register are

both zero. SMD is normally only accessed during initialization. This register is byte addressable.

Table 32 presents the serial mode select clock mode bits.

Table 31. Serial Mode Register

SCM2

SCM1

SCM0

NRZI

LOOP

PFS

NFCS

Bit [7]—SCM2 → (SMD.7) Select clock mode—Bit [2].

Bit [6]—SCM1 → (SMD.6) Select clock mode—Bit [1].

Bit [5]—SCM0 → (SMD.5) Select clock mode—Bit [0].

Bit [4]—NRZI → (SMD.4) When set selects NRZI encoding otherwise NRZ.

Bit [3]—LOOP → (SMD.3) When set, selects loop configuration, else point-to-point

mode.

Bit [2]—PFS → (SMD.2) Pre-frame sync mode. When set, causes two bytes to be

transmitted before the first flag of the frame for DPLL synchronization. If NRZI is set,

00H is transmitted, otherwise 55H. This ensures that 16 transitions are sent before the

opening flag.

Bit [1]—NB → (SMD.1) Non-buffered mode. No control field contained in SDLC frame.

Bit [0]—NFCS → (SMD.0) When set, selects No FCS field contained in the SDLC frame.

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