Normal Mode (Crb(Mod) = 0); Operating Modes; Network Mode (Crb(Mod) = 1; Cra(Dc) ≠ 00000); Figure 7-21 Essi Main Modes - Motorola DSP56305 User Manual

7.5.3

Operating Modes

The ESSI has three basic operating modes and several data/operation formats. These
modes can be programmed using the ESSI Control Registers. The data/operation
formats available to the ESSI are selected by setting or clearing control bits in the CRA
and CRB. These control bits are WL[2:1], MOD, SYN, FSL[1:0], FSR, FSP, CKP, and
SHFD.
Normal
Mode
7.5.3.1

Normal Mode (CRB(MOD) = 0)

Normal mode is typically used to transfer data to or from a single device. Selecting the
Normal mode is accomplished by clearing the MOD bit in the CRB. In Normal mode, the
ESSI sends or receives one data word per frame (per enabled receiver or transmitter).
The transfers are periodic.
Network Mode (CRB(MOD) = 1; CRA(DC) ≠ 00000)
7.5.3.2
The ESSI's Network mode is well-suited for using the DSP in Time Division
Multiplexing (TDM) networks, or in parallel processing networks.
In Network mode, the ESSI may be programmed for two to thirty-two time slots per
frame (always the same number for receive and transmit). A single data word may be
received or transmitted (from each enabled receiver or transmitter) during each time
slot. The duration of a receive or transmit time slot equals the time needed to shift one
word in or out of the ESSI, respectively. In other words, if the word size is 24 bits, one
time slot consists of exactly 24 ESSI clock periods ("bit times"). An edge on the receive or
transmit frame sync signal (rising or falling edge, but never both) indicates the
beginning of a new data frame.
MOTOROLA
Enhanced Synchronous Serial Interface (ESSI)
ESSI
0 1
MOD
1-31
CRB
Network
Mode

Figure 7-21 ESSI Main Modes

DSP56305 User's Manual
Operating Modes
0
DC[4:0]
On-Demand
CRA
Mode
AA1427
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