- •Table of Contents
- •INTRODUCTION TO THE DSP56002
- •DSP56002 PIN DESCRIPTIONS
- •PORT A
- •PORT B
- •PORT C
- •PROGRAMMING SHEETS
- •List of Figures
- •List of Tables
- •1.1 INTRODUCTION
- •Figure 1-1 DSP56002 Technical Literature
- •1.2 FEATURES
- •Zero Overhead Nested DO Loops
- •512 x 24 Program RAM
- •Two 256 x 24 Data RAM
- •Two 256 x 24 Data ROM (Sine and Cosine Tables)
- •Synchronous Serial Interface Port
- •24 General Purpose I/O Pins
- •24-bit Timer/Event Counter
- •1.3 DSP56K CENTRAL PROCESSING UNIT OVERVIEW
- •Data Buses
- •Address Buses
- •Data Arithmetic Logic Unit (data ALU)
- •Address Generation Unit (AGU)
- •Program Control Unit (PCU)
- •Memory Expansion (Port A)
- •Figure 1-2 DSP56002 Block Diagram
- •1.4 MANUAL ORGANIZATION
- •INTRODUCTION TO THE DSP56002
- •2.1 INTRODUCTION
- •2.2 SIGNAL DESCRIPTIONS
- •Figure 2-1 DSP56002 Signals
- •2.2.1 Port A Address and Data Bus
- •2.2.2 Port A Bus Control
- •Table 2-1 Program and Data Memory Select Encoding
- •2.2.3 Interrupt and Mode Control
- •2.2.4 Power and Clock
- •2.2.5 Host Interface
- •2.2.6 Serial Communication Interface (SCI)
- •2.2.7 Synchronous Serial Interface (SSI)
- •2.3 ON-CHIP EMULATION (OnCE) PINS
- •2.3.1 Debug Serial Input/Chip Status 0 (DSI/OS0)
- •2.3.2 Debug Serial Clock/Chip Status 1 (DSCK/OS1)
- •2.3.3 Debug Serial Output (DSO)
- •2.3.4 Debug Request Input (DR)
- •2.4 PLL PINS
- •2.5 TIMER/EVENT COUNTER MODULE PIN
- •SECTION 2
- •DSP56002 PIN DESCRIPTIONS
- •3.1 MEMORY MODULES AND OPERATING MODES
- •3.2 DSP56002 DATA AND PROGRAM MEMORY
- •3.2.1 Program Memory
- •3.2.2 X Data Memory
- •3.2.3 Y Data Memory
- •Figure 3-1 DSP56002 Memory Maps
- •3.3 DSP56002 OPERATING MODE REGISTER (OMR)
- •3.3.1 Chip Operating Mode (Bits 0 and 1)
- •Figure 3-2 OMR Format
- •3.3.2 Data ROM Enable (Bit 2)
- •3.3.3 Internal Y Memory Disable Bit (Bit 3)
- •Table 3-1 Memory Mode Bits
- •3.3.4 Chip Operating Mode (Bit 4)
- •3.3.5 Reserved (Bit 5)
- •3.3.6 Stop Delay (Bit 6)
- •3.4 DSP56002 OPERATING MODES
- •Table 3-2 DSP56002 Operating Mode Summary
- •3.4.1 Single Chip Mode (Mode 0)
- •3.4.2 Bootstrap From EPROM (Mode 1)
- •Figure 3-3 Port A Bootstrap Circuit
- •Table 3-3 Organization of EPROM Data Contents
- •3.4.3 Normal Expanded Mode (Mode 2)
- •3.4.4 Development Mode (Mode 3)
- •3.4.5 Reserved (Mode 4)
- •3.4.6 Bootstrap From Host (Mode 5)
- •3.4.7 Bootstrap From SCI (Mode 6)
- •3.4.8 Reserved (Mode 7)
- •3.5 DSP56002 INTERRUPT PRIORITY REGISTER
- •Table 3-4 Interrupt Vectors
- •Table 3-5 Exception Priorities Within an IPL
- •SECTION 3
- •4.1 INTRODUCTION
- •4.2 PORT A INTERFACE
- •Figure 4-1 Port A Signals
- •Figure 4-2 External Program Space
- •Figure 4-3 External X and Y Data Space
- •Figure 4-4 Memory Segmentation
- •Table 4-1 Program and Data Memory Select Encoding
- •4.3 PORT A TIMING
- •Figure 4-8 Mixed-Speed Expanded System
- •4.4 PORT A WAIT STATES
- •Table 4-2 Wait State Control
- •4.5 BUS CONTROL REGISTER (BCR)
- •Figure 4-9 Bus Control Register
- •Figure 4-10 Bus Strobe/Wait Sequence
- •4.6 BUS STROBE AND WAIT PINS
- •4.7 BUS ARBITRATION AND SHARED MEMORY
- •Figure 4-11 Bus Request/Bus Grant Sequence
- •Table 4-3 BR and BG During WAIT
- •1. DSP# 2 sets OUT1=0 (BR#1=0).
- •4.7.4 Signaling Using Semaphores
- •Figure 4-17 Signaling Using Semaphores
- •5.1 INTRODUCTION
- •Figure 5-1 Port B Interface
- •5.2 GENERAL PURPOSE I/O CONFIGURATION
- •Figure 5-2 Parallel Port B Registers
- •Figure 5-3 Parallel Port B Pinout
- •Figure 5-4 Port B I/O Pin Control Logic
- •5.2.1 Programming General Purpose I/O
- •Figure 5-5 On-Chip Peripheral Memory Map
- •5.2.2 Port B General Purpose I/O Timing
- •Figure 5-7 I/O Port B Configuration
- •5.3 HOST INTERFACE (HI)
- •Figure 5-8 HI Block Diagram
- •5.3.1 Host Interface – DSP CPU Viewpoint
- •5.3.2 Programming Model – DSP CPU Viewpoint
- •5.3.2.1 Host Control Register (HCR)
- •5.3.2.1.4 HCR Host Flag 2 (HF2) Bit 3
- •5.3.2.1.5 HCR Host Flag 3 (HF3) Bit 4
- •5.3.2.1.6 HCR Reserved Control (Bits 5, 6, and 7)
- •5.3.2.2 Host Status Register (HSR)
- •5.3.2.2.1 HSR Host Receive Data Full (HRDF) Bit 0
- •5.3.2.2.3 HSR Host Command Pending (HCP) Bit 2
- •5.3.2.2.4 HSR Host Flag 0 (HF0) Bit 3
- •5.3.2.2.5 HSR Host Flag 1 (HF1) Bit 4
- •Figure 5-10 Host Flag Operation
- •5.3.2.2.6 HSR Reserved Status (Bits 5 and 6)
- •5.3.2.2.7 HSR DMA Status (DMA) Bit 7
- •5.3.2.3 Host Receive Data Register (HRX)
- •5.3.2.4 Host Transmit Data Register (HTX)
- •5.3.2.5 Register Contents After Reset
- •5.3.2.6 Host Interface DSP CPU Interrupts
- •Figure 5-11 HSR–HCR Operation
- •5.3.2.7 Host Port Usage Considerations – DSP Side
- •5.3.3 Host Interface – Host Processor Viewpoint
- •Figure 5-13 HI Register Map
- •5.3.3.2 Interrupt Control Register (ICR)
- •5.3.3.2.1 ICR Receive Request Enable (RREQ) Bit 0
- •5.3.3.2.3 ICR Reserved Bit (Bit 2)
- •Table 5-2 HREQ Pin Definition
- •5.3.3.2.4 ICR Host Flag 0 (HF0) Bit 3
- •5.3.3.2.5 ICR Host Flag 1 (HF1) Bit 4
- •Table 5-3 Host Mode Bit Definition
- •5.3.3.2.7 ICR Initialize Bit (INIT) Bit 7
- •Table 5-4 HREQ Pin Definition
- •5.3.3.3 Command Vector Register (CVR)
- •Figure 5-14 Command Vector Register
- •5.3.3.3.2 CVR Reserved Bit (Bit 6)
- •5.3.3.3.3 CVR Host Command Bit (HC) Bit 7
- •5.3.3.4 Interrupt Status Register (ISR)
- •5.3.3.4.3 ISR Transmitter Ready (TRDY) Bit 2
- •5.3.3.4.4 ISR Host Flag 2 (HF2) Bit 3
- •5.3.3.4.5 ISR Host Flag 3 (HF3) Bit 4
- •5.3.3.4.6 ISR Reserved Bit (Bit 5)
- •5.3.3.4.7 ISR DMA Status (DMA) Bit 6
- •5.3.3.4.8 ISR Host Request (HREQ) Bit 7
- •5.3.3.5 Interrupt Vector Register (IVR)
- •5.3.3.6 Receive Byte Registers (RXH, RXM, RXL)
- •5.3.3.7 Transmit Byte Registers (TXH, TXM, TXL)
- •5.3.3.8 Registers After Reset
- •Table 5-5 Host Registers after Reset (Host Side)
- •5.3.4 Host Interface Pins
- •5.3.4.3 Host Read/Write (HR/W)
- •5.3.4.4 Host Enable (HEN)
- •5.3.4.5 Host Request (HREQ)
- •Table 5-6 Port B Pin Definitions
- •5.3.4.6 Host Acknowledge (HACK)
- •5.3.5 Servicing the Host Interface
- •Figure 5-15 Host Processor Transfer Timing
- •1. Polling
- •2. Interrupts, which can be either
- •5.3.5.1 HI Host Processor Data Transfer
- •5.3.5.2 HI Interrupts Host Request (HREQ)
- •Figure 5-16 Interrupt Vector Register Read Timing
- •5.3.5.3 Polling
- •Figure 5-17 HI Interrupt Structure
- •Figure 5-18 DMA Transfer Logic and Timing
- •5.3.5.5 Servicing DMA Interrupts
- •5.3.6 HI Application Examples
- •5.3.6.1 HI Initialization
- •Figure 5-19 HI Initialization Flowchart
- •Figure 5-20 HI Initialization–DSP Side
- •Figure 5-21 (a) HI Configuration–Host Side
- •Figure 5-22 Host Mode and INIT Bits
- •2. Assert HACK If the interface is using HACK
- •5. Assert HEN to enable the HI
- •5.3.6.2.1 Host to DSP - Data Transfer
- •Figure 5-23 Bits Used for Host-to-DSP Transfer
- •Figure 5-24 Data Transfer from Host to DSP
- •5. Writing data to TXL clears TXDE in the ISR.
- •5.3.6.2.2 Host to DSP – Command Vector
- •Figure 5-27 HI Exception Vector Locations
- •Figure 5-28 Host Command
- •2. The HC is then set.
- •3. The HCP bit in the HSR is set when HC is set.
- •Figure 5-25 Receive Data from Host–Main Program
- •Figure 5-29 Bootstrap Using the HI
- •Figure 5-30 Transmit/Receive Byte Registers
- •Figure 5-31 Bootstrap Code Fragment
- •5.3.6.2.4 DSP to Host Data Transfer
- •Figure 5-32 Bits Used for DSP to Host Transfer
- •Figure 5-33 Data Transfer from DSP to Host
- •5.3.6.3 DMA Data Transfer
- •Figure 5-36 HI Hardware–DMA Mode
- •5.3.6.3.1 Host To DSP Internal Processing
- •1. HI asserts the HREQ pin when TXDE=1.
- •Figure 5-37 DMA Transfer and Host Interrupts
- •3. When HACK is asserted, the HI deasserts HREQ.
- •Figure 5-39 Host-to-DSP DMA Procedure
- •Figure 5-38 Host Bits with TREQ and RREQ
- •5.3.6.3.2 Host to DSP DMA Procedure
- •5.3.6.3.3 DSP to Host Internal Processing
- •5.3.6.3.4 DSP to Host DMA Procedure
- •Figure 5-40 DSP to Host DMA Procedure
- •5.3.6.4 Example Circuits
- •Figure 5-41 MC68HC11 to DSP56002 Host Interface
- •Figure 5-42 MC68000 to DSP56002 Host Interface
- •Figure 5-43 Multi-DSP Network Example
- •2. Overwriting Transmit Byte Registers:
- •4. Overwriting the Host Vector:
- •5. Cancelling a Pending Host Command Exception:
- •6.1 INTRODUCTION
- •Figure 6-1 Port C Interface
- •6.2 GENERAL-PURPOSE I/O (PORT C)
- •Figure 6-2 Port C GPIO Control
- •Figure 6-3 Port C GPIO Registers
- •Figure 6-4 Port C I/O Pin Control Logic
- •6.2.1 Programming General Purpose I/O
- •Figure 6-6 Write/Read Parallel Data with Port C
- •Figure 6-7 I/O Port C Configuration
- •6.2.2 Port C General Purpose I/O Timing
- •6.3 SERIAL COMMUNICATION INTERFACE (SCI)
- •6.3.1 SCI I/O Pins
- •6.3.1.1 Receive Data (RXD)
- •6.3.1.2 Transmit Data (TXD)
- •6.3.1.3 SCI Serial Clock (SCLK)
- •6.3.2 SCI Programming Model
- •Figure 6-9 SCI Programming Model
- •6.3.2.1 SCI Control Register (SCR)
- •Figure 6-10 Serial Formats (Sheet 1 of 2)
- •Table 6-1 Word Formats
- •6.3.2.1.2 SCR SCI Shift Direction (SSFTD) Bit 3
- •6.3.2.1.3 SCR Send Break (SBK) Bit 4
- •6.3.2.1.4 SCR Wakeup Mode Select (WAKE) Bit 5
- •6.3.2.1.5 SCR Receiver Wakeup Enable (RWU) Bit 6
- •6.3.2.1.7 SCR Receiver Enable (RE) Bit 8
- •6.3.2.1.8 SCR Transmitter Enable (TE) Bit 9
- •6.3.2.1.14 SCR SCI Clock Polarity (SCKP) Bit 15
- •6.3.2.2 SCI Status Register (SSR)
- •6.3.2.2.1 SSR Transmitter Empty (TRNE) Bit 0
- •6.3.2.2.4 SSR Idle Line Flag (IDLE) Bit 3
- •6.3.2.2.5 SSR Overrun Error Flag (OR) Bit 4
- •6.3.2.2.6 SSR Parity Error (PE) Bit 5
- •6.3.2.2.7 SSR Framing Error Flag (FE) Bit 6
- •6.3.2.2.8 SSR Received Bit 8 Address (R8) Bit 7
- •6.3.2.3 SCI Clock Control Register (SCCR)
- •Figure 6-11 16 x Serial Clock
- •6.3.2.3.2 SCCR Clock Out Divider (COD) Bit 12
- •6.3.2.3.3 SCCR SCI Clock Prescaler (SCP) Bit 13
- •Figure 6-12 SCI Baud Rate Generator
- •6.3.2.4 SCI Data Registers
- •6.3.2.4.1 SCI Receive Registers
- •Figure 6-13 Data Packing and Unpacking
- •6.3.2.4.2 SCI Transmit Registers
- •6.3.3 Register Contents After Reset
- •6.3.4 SCI Initialization
- •Figure 6-14 SCI Initialization Procedure
- •6.3.5 SCI Exceptions
- •Figure 6-16 SCI Exception Vector Locations
- •6.3.6 Synchronous Data
- •Figure 6-18 Synchronous Slave
- •Figure 6-19 Synchronous Timing
- •Figure 6-20 SCI Synchronous Transmit
- •Figure 6-21 SCI Synchronous Receive
- •6.3.7 Asynchronous Data
- •6.3.7.1 Asynchronous Data Reception
- •6.3.7.2 Asynchronous Data Transmission
- •Figure 6-27 Transmitting Marks and Spaces
- •6.3.8 Multidrop
- •6.3.8.1 Transmitting Data and Address Characters
- •6.3.8.3 Idle Line Wakeup
- •Figure 6-32 Idle Line Wakeup
- •6.3.8.4 Address Mode Wakeup
- •6.3.8.5 Multidrop Example
- •6.3.9 SCI Timer
- •Figure 6-35 SCI Timer Operation
- •Figure 6-36 SCI Timer Example (Sheet 1 of 2)
- •Figure 6-37 DSP56002 Bootstrap Example - Mode 6
- •Figure 6-38 Bootstrap Code Fragment
- •6.3.11 Example Circuits
- •Figure 6-39 Synchronous Mode Example
- •Figure 6-41 Multimaster System Example
- •Figure 6-40 Master-Slave System Example
- •6.4 SYNCHRONOUS SERIAL INTERFACE (SSI)
- •6.4.1 SSI Data and Control Pins
- •6.4.1.1 Serial Transmit Data Pin (STD)
- •6.4.1.2 Serial Receive Data Pin (SRD)
- •6.4.1.3 Serial Clock (SCK)
- •6.4.1.4 Serial Control Pin (SC0)
- •Table 6-7 SSI Operation: Flag 0 and Rx Clock
- •6.4.1.5 Serial Control Pin (SC1)
- •Table 6-8 SSI Operation: Flag 1 and Rx Frame Sync
- •6.4.1.6 Serial Control Pin (SC2)
- •Table 6-9 SSI Operation: Tx and Rx Frame Sync
- •6.4.2 SSI Programming Model
- •Figure 6-45 SSI Programming Model (Sheet 1 of 2)
- •6.4.2.1 SSI Control Register A (CRA)
- •Table 6-10 Number of Bits/Word
- •6.4.2.1.4 CRA Prescaler Range (PSR) Bit 15
- •6.4.2.2 SSI Control Register B (CRB)
- •6.4.2.2.1 CRB Serial Output Flag 0 (OF0) Bit 0
- •6.4.2.2.2 CRB Serial Output Flag 1 (OF1) Bit 1
- •Figure 6-46 Serial Control, Direction Bits
- •6.4.2.2.6 CRB Clock Source Direction (SCKD) Bit 5
- •6.4.2.2.7 CRB Shift Direction (SHFD) Bit 6
- •Table 6-11 Frame Sync Length
- •6.4.2.2.9 CRB Sync/Async (SYN) Bit 9
- •6.4.2.2.10 CRB Gated Clock Control (GCK) Bit 10
- •6.4.2.2.11 CRB SSI Mode Select (MOD) Bit 11
- •6.4.2.2.12 CRB SSI Transmit Enable (TE) Bit 12
- •6.4.2.2.13 CRB SSI Receive Enable (RE) Bit 13
- •6.4.2.3 SSI Status Register (SSISR)
- •6.4.2.3.1 SSISR Serial Input Flag 0 (IF0) Bit 0
- •6.4.2.3.2 SSISR Serial Input Flag 1 (IF1) Bit 1
- •6.4.2.3.9 SSI Receive Shift Register
- •Figure 6-47 Receive Data Path
- •6.4.2.3.10 SSI Receive Data Register (RX)
- •6.4.2.3.11 SSI Transmit Shift Register
- •Figure 6-48 Transmit Data Path
- •6.4.2.3.12 SSI Transmit Data Register (TX)
- •6.4.2.3.13 Time Slot Register (TSR)
- •6.4.3 Operational Modes and Pin Definitions
- •6.4.4 Registers After Reset
- •Table 6-14 SSI Registers After Reset
- •6.4.5 SSI Initialization
- •Figure 6-49 SSI Initialization Block Diagram
- •Figure 6-50 SSI CRA Initialization Procedure
- •Figure 6-51 SSI CRB Initialization Procedure
- •Figure 6-52 SSI Initialization Procedure
- •6.4.6 SSI Exceptions
- •Figure 6-53 SSI Exception Vector Locations
- •Figure 6-54 SSI Exceptions
- •Table 6-17 SSI Operating Modes
- •6.4.7.1 Data/Operation Formats
- •6.4.7.1.1 Normal/Network Mode Selection
- •6.4.7.1.2 Continuous/Gated Clock Selection
- •Figure 6-58 CRB GCK Bit Operation
- •Figure 6-62 Synchronous Communication
- •Figure 6-63 CRB SYN Bit Operation
- •Figure 6-64 Gated Clock — Synchronous Operation
- •6.4.7.1.4 Frame Sync Selection
- •Figure 6-68 CRB FSL0 and FSL1 Bit Operation
- •6.4.7.1.5 Shift Direction Selection
- •Figure 6-71 CRB SHFD Bit Operation (Sheet 1 of 2)
- •6.4.7.2 Normal Mode Examples
- •6.4.7.2.1 Normal Mode Transmit
- •Figure 6-72 Normal Mode Example
- •2. SC2 is TX and RX frame sync out
- •3. STD is transmit data out
- •4. SCK clocks the transmit data out
- •6.4.7.2.2 Normal Mode Receive
- •6.4.7.3 Network Mode Examples
- •Figure 6-75 Network Mode Example
- •Figure 6-76 TDM Network Software Flowchart
- •Figure 6-77 Network Mode Initialization
- •6.4.7.3.1 Network Mode Transmit
- •6.4.7.3.2 Network Mode Receive
- •Figure 6-80 On Demand Example
- •Figure 6-81 On-Demand Data-Driven Network Mode
- •Figure 6-82 Clock Modes
- •Figure 6-83 SPI Configuration
- •6.4.8 Flags
- •Figure 6-88 Output Flag Example
- •Figure 6-89 Output Flag Initialization
- •Figure 6-90 Input Flags
- •6.4.9 Example Circuits
- •Figure 6-91 SSI Cascaded Multi-DSP System
- •Figure 6-92 SSI TDM Parallel DSP Network
- •Figure 6-96 SSI TDM Bus DSP Network
- •SECTION 6
- •PORT C
- •7.1 INTRODUCTION
- •7.2 TIMER/EVENT COUNTER BLOCK DIAGRAM
- •Figure 7-2 Timer/Event Counter Programming Model
- •7.3 TIMER COUNT REGISTER (TCR)
- •7.4 TIMER CONTROL/STATUS REGISTER (TCSR)
- •7.4.1 Timer Enable (TE) Bit 0
- •7.4.2 Timer Interrupt Enable (TIE) Bit 1
- •7.4.3 Inverter (INV) Bit 2
- •Table 7-1 Timer/Event Counter Control Bits
- •GPIO*
- •Internal
- •Timer (Mode 0)
- •Output
- •Internal
- •Timer Pulse (Mode 1)
- •Output
- •Internal
- •Timer Toggle (Mode 2)
- •Reserved - Do Not Use
- •Input
- •Internal
- •Input Width (Mode 4)
- •Input
- •Internal
- •Input Period (Mode 5)
- •Input
- •External
- •Standard Time Counter (Mode 6)
- •Input
- •External
- •Event Counter (Mode 7)
- •7.4.5 General Purpose I/O (GPIO) Bit 6
- •7.4.6 Timer Status (TS) Bit 7
- •7.4.7 Direction (DIR) Bit 8
- •7.4.8 Data Input (DI) Bit 9
- •7.4.9 Data Output (DO) Bit 10
- •7.4.10 TCSR Reserved bits (Bits 11-23)
- •7.5 TIMER/EVENT COUNTER MODES OF OPERATION
- •Figure 7-3 Standard Timer Mode (Mode 0)
- •Figure 7-4 Timer/Event Counter Disable
- •7.5.4 Timer Mode 4 (Pulse Width Measurement Mode)
- •Figure 7-8 Pulse Width Measurement Mode (INV=0)
- •Figure 7-9 Pulse Width Measurement Mode (INV=1)
- •7.5.5 Timer Mode 5 (Period Measurement Mode)
- •Figure 7-10 Period Measurement Mode (INV=0)
- •Figure 7-11 Period Measurement Mode (INV=1)
- •7.7 OPERATING CONSIDERATIONS
- •7.8 SOFTWARE EXAMPLES
- •7.8.1 General Purpose I/O Input
- •7.8.2 General Purpose I/O Output
- •7.8.4 Pulse Width Measurement Mode (Timer Mode 4)
- •7.8.5 Period Measurement Mode (Timer Mode 5)
- •A.1 INTRODUCTION
- •Table B-2 Instruction Set Summary — Sheet 1 of 5
- •Figure B-2 Status Register (SR)
- •Figure B-3 Bus Control Register (BCR)
- •Figure B-7 Port B Control Register (PBC)
- •Figure B-8 Port B Data Direction Register (PBDDR)
- •Figure B-9 Port B Data Register (PBD)
- •Figure B-10 Port C Control Register (PCC)
- •Figure B-12 Port C Data Register (PCD)
- •Figure B-17 Host Transmit Data Register (HTX)
- •Figure B-13 Port B Control Register (PBC)
- •Figure B-14 Host Control Register (HCR)
- •Figure B-16 Host Receive Data Register (HRX)
- •Figure B-15 Host Status Register (HSR)
- •Figure B-19 Command Vector Register (CVR)
- •Figure B-18 Interrupt Control Register (ICR)
- •Figure B-20 Interrupt Status Register (ISR)
- •Figure B-21 Interrupt Vector Register (IVR)
- •Figure B-24 Port C Control Register (PCC)
- •Figure B-25 SCI Control Register (SCR)
- •Figure B-27 SCI Clock Control Register (SCCR)
- •Figure B-29 SCI Receive Data Registers
- •Figure B-28 SCI Transmit Data Registers
- •Figure B-30 SSI Control Register (PCC)
- •Figure B-31 SSI Control Register A (CRA)
- •Figure B-32 SSI Control Register B (CRB)
- •Figure B-33 SSI Status Register (SSISR)
- •Figure B-35 Timer Count Register (TCR)
- •INDEX
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Freescale Semiconductor, Inc.
SERIAL COMMUNICATION INTERFACE (SCI)
6.3.2.3.2SCCR Clock Out Divider (COD) Bit 12
Figure 6-12 and Figure 6-35 show the clock divider circuit. The output divider is controlled by COD and the SCI mode. If the SCI mode is synchronous, the output divider is fixed at divide by 2; if the SCI mode is asynchronous, and
1.If COD equals zero and SCLK is an output (i.e., TCM and RCM=0), the SCI
clock is divided by 16 before being output to the SCLK pin; thus, the SCLK output is a 1 × clock
2.If COD equals one and SCLK is an output, the SCI clock is fed directly out to the SCLK pin; thus, the SCLK output is a 16 × baud clock
The COD bit is cleared by hardware and software reset.
6.3.2.3.3SCCR SCI Clock Prescaler (SCP) Bit 13
The SCI SCP bit selects a divide by 1 (SCP=0) or divide by 8 (SCP=1) prescaler for the clock divider. The output of the prescaler is further divided by 2 to form the SCI clock. Hardware and software reset clear SCP. Figure 6-12 and Figure 6-35 show the clock divider diagram.
6.3.2.3.4SCCR Receive Clock Mode Source Bit (RCM) Bit 14
RCM selects internal or external clock for the receiver (see Figure 6-35). RCM equals zero selects the internal clock; RCM equals one selects the external clock from the SCLK pin. Hardware and software reset clear RCM.
6.3.2.3.5SCCR Transmit Clock Source Bit (TCM) Bit 15
The TCM bit selects internal or external clock for the transmitter (see Figure 6-35). TCM equals zero selects the internal clock; TCM equals one selects the external clock from the SCLK pin. Hardware and software reset clear TCM.
6.3.2.4SCI Data Registers
The SCI data registers are divided into two groups: receive and transmit. There are two receive registers – a receive data register (SRX) and a serial-to-parallel receive shift register. There are also two transmit registers – a transmit data register (called either STX or STXA) and a parallel-to-serial transmit shift register.
6.3.2.4.1SCI Receive Registers
Data words received on the RXD pin are shifted into the SCI receive shift register. When the complete word has been received, the data portion of the word is transferred to the byte-wide SRX. This process converts the serial data to parallel data and provides double
6 - 26 PORT C MOTOROLA
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SERIAL COMMUNICATION INTERFACE (SCI)
buffering. Double buffering provides flexibility and increased throughput since the programmer can save the previous word while the current word is being received.
The SRX can be read at three locations: X:$FFF4, X:$FFF5, and X:$FFF6 (see Figure 6-13). When location X:$FFF4 is read, the contents of the SRX are placed in the lower byte of the data bus and the remaining bits on the data bus are written as zeros. Similarly, when X:$FFF5 is read, the contents of SRX are placed in the middle byte of the bus, and when X:$FFF6 is read, the contents of SRX are placed in the high byte with the remaining bits zeroed. Mapping SRX as described allows three bytes to be efficiently packed into
TCM |
RCM |
TX Clock |
RX Clock |
SCLK Pin |
Mode |
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0 |
0 |
Internal |
Internal |
Output |
Synchronous/Asynchronous |
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0 |
1 |
Internal |
External |
Input |
Asynchronous Only |
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1 |
0 |
External |
Internal |
Input |
Asynchronous Only |
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fosc
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12-BIT COUNTER |
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1 or 8 |
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CD11 - CD0 |
SCP |
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INTERNAL CLOCK |
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DIVIDE |
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BY 16 |
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SCI CORE LOGIC |
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USES DIVIDE BY 16 FOR |
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ASYNCHRONOUS |
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USES DIVIDE BY 2 FOR |
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STIR |
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IF ASYNCHRONOUS |
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TIMER |
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DIVIDE BY 1 OR 16 |
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INTERRUPT |
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COD |
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IF SYNCHRONOUS |
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DIVIDE BY 2 |
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fo |
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BPS = 64 |
x (7(SCP) + 1) x CD + 1) |
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SCKP |
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SCKP = 0 |
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+ |
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where: SCP = 0 or 1 |
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SCKP = 1 |
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CD = 0 to $FFF |
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TO SCLK |
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Figure 6-12 SCI Baud Rate Generator
MOTOROLA PORT C 6 - 27
For More Information On This Product, Go to: www.freescale.com