8-Bit Software Serial Transmitter Datasheet TX8SWV 1.2
001-16838 Rev. *L
8-Bit Software Serial Transmitter
Copyright © 2008-2013 Cypress Semiconductor Corporation. All Rights Reserved.
PSoC Blocks
Resources
Digital
Analog CT
API Memory (Bytes)
Analog SC
Flash
Pins (per
External I/O
and Clock)
RAM
CY8C29/27/24/21xxx, CY8C20x34, CY8CLED02/04/08/16, CY8CLED0xD, CY8CLED0xG, CY8C20x66,
CY8C20x36, CY8C20336AN, CY8C20436AN, CY8C20636AN, CY8C20XX6L,.CY8C20xx6AS, CY8C20x46,
CY8C20x96, CY7C604xx, CY7C643xx, CYONS2xxx, CYONSTB2010, CYONSTB2011, CYONSFN2010-BFXC,
CYONSCN2024-BFXC, CYONSCN2028-BFXC, CYONSCN2020-BFXC, CYONSKN2033-BFXC, CYONSKN2035BFXC, CYONSKN2030-BFXC, CY8CTMG2xx, CY8CTMA30xx, CY8C28x45, CY8C21x12,
CYONSTN2040,CY8CTMA140, CY8C20xx7/7S, CYRF89x35, CY8C20065, CY8C24x93, CY7C69xxx
0
0
0
383
2
1
For one or more fully configured, functional example projects that use this user module go to
www.cypress.com/psocexampleprojects
Features and Overview
7/8-bit software serial transmitter
Data framing consists of start, optional parity, and one or two stop bits
RS-232 serial-data compatible format with optional parity
The TX8SW User Module is an 7- or 8-bit RS-232 data-format compliant serial transmitter. The data
transmitted is framed with a leading start bit and a final one or two stop bits. Transmitter firmware is used
to start and stop device and control transmission of complex structures like strings, HEX value
representations, and so on.
Figure 1.
TX8SW Block Diagram
Functional Description
The TX8SW User Module is an RS-232 data-format compliant software serial transmitter. The transmitter
supports 115200, 57600, 38400, 19200, 9600, 4800, 2400, and 1200 bps transfer speed with or without
parity. It does not use any PSoC blocks and can be used when all digital resources are occupied.
Transmitter firmware is used to start and stop the user module and to write data to the dedicated pin.
During transmission, the user module masks interrupt and change the CPU clock frequency to assure the
proper timing of signals. Interrupts and CPU frequency are restored after the byte is sent. The SysClk
does not change and change of the CPU clock does not affect the hardware resource clock during
transmission.
Cypress Semiconductor Corporation
Document Number: 001-16838 Rev. *L
•
198 Champion Court
•
San Jose, CA 95134-1709
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408-943-2600
Revised May 30, 2013
8-Bit Software Serial Transmitter
For all baud rates used, the CPU clock is less than 3 MHz. All supported baud rates are available
regardless of the current CPU clock. IMO settings are detected using conditional compiler directives. The
TX8SW User Module works with all IMO settings (24/12/6MHz). All CPU clock changes and previous
value restores are completed by TX8SW routines and do not require manual frequency changes. The
following tables show the CPU clock and CPU cycles used for different combinations of baud rate and
SysClock:
Table 1.
CPU Clock Used for Byte Transmit Time
Baud Rate
SysClock
115200
57600
38400
19200
9600
4800
2400
1200
24 MHz (Note 1)
3 MHz
1.5 MHz
1.5 MHz
0.75 MHz 0.75 MHz 187 kHz
93 kHz
93 kHz
12 MHz
(Note 2)
3 MHz
1.5 MHz
1.5 MHz
0.75 MHz 375 kHz
375 kHz
93 kHz
46 kHz
6 MHz
(Note 3)
3 MHz
1.5 MHz
1.5 MHz
0.75 MHz 375 kHz
187 kHz
187 kHz
46 kHz
4800
2400
1200
Table 2.
CPU Cycles per One Bit Transfer
Baud Rate
SysClock
115200
57600
38400
19200
9600
24 MHz
(Note 1)
26
26
39
39
78
39
39
78
12 MHz (Note 2)
26
26
39
39
39
78
39
39
6 MHz
(Note 3)
26
26
39
39
39
39
78
39
Note
1. Not available in CY8C20x34 parts.
2. Not available in CY7C64215, CY8C24x94, CY8C27xxx, CY8C29xxx, or CY8CLED04/08/16 parts.
3. Not available in CY7C64215, CY8C24x94, CY8C27xxx or CY8CLED04/08 parts.
During transmit time interrupts are masked. The following table shows the delay introduced before ISR for
each baud rate selection:
Document Number: 001-16838 Rev. *L
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8-Bit Software Serial Transmitter
Table 3.
Interrupt Latency Table
Baud Rate
Min (Note 1)
Typ2 (Note 2)
Max3(Note 3)
Units
115200
69.4
78.1
95.5
µs
57600
139
156
191
µs
38400
208
234
286
µs
19200
417
469
573
µs
9600
833
938
1145
µs
4800
1.66
1.88
2.29
ms
2400
3.33
3.75
4.58
ms
1200
6.67
7.50
9.17
ms
Note
1. For 7-bit data format, one stop bit and no parity.
2. For 8-bit data format, one stop bit and no parity.
3. For 8-bit data format, two stop bits and parity bit.
DC and AC Electrical Characteristics
Table 4.
DC and AC Electrical Characteristics
Parameter
Value
Units
Conditions and Notes (See Note)
F115200
115385
baud
When SysCPU is 24/12/6 MHz exactly
F57600
57692
baud
When SysCPU is 24/12/6 MHz exactly
F38400
38462
baud
When SysCPU is 24/12/6 MHz exactly
F19200
19231
baud
When SysCPU is 24/12/6 MHz exactly
F9600
9615
baud
When SysCPU is 24/12/6 MHz exactly
F4800
4808
baud
When SysCPU is 24/12/6 MHz exactly
F2400
2404
baud
When SysCPU is 24/12/6 MHz exactly
F1200
1202
baud
When SysCPU is 24/12/6 MHz exactly
Note
Information about IMO tolerances can be found in the datasheet for your chosen device.
Parameters and Resources
Port
Select the port to send data out.
Pin
Select which pin of the selected port to send data out.
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8-Bit Software Serial Transmitter
BaudRate
Select baud rate from the list. Possible choices are 115200, 57600, 38400, 19200, 9600, 4800, 2400
and 1200 bits per second.
Parity
Select parity type from the list. The choices are Odd, Even, and None.
StopBits
Select the number of stop bits from the list. One or two stop bits are supported.
DataBits
Select the number of data bits from the list. Seven or eight data bits are supported.
Placement
The TX8SW User Module does not require any digital or analog PSoC blocks. There are no placement
restrictions.
Application Programming Interface
The Application Programming Interface (API) routines are provided as part of the user module to allow the
designer to deal with the module at a higher level. This section specifies the interface to each function
together with related constants provided by the “include” files.
Each time a user module is placed, it is assigned an instance name. By default, PSoC Designer assigns
TX8SW_1 to the first instance of this user module in a given project. It can be changed to any unique
value that follows the syntactic rules for identifiers. The assigned instance name becomes the prefix of
every global function name, variable and constant symbol. In the following descriptions the instance name
has been shortened to TX8SW for simplicity.
** In this, as in all user module APIs, the values of the A and X register may be altered by calling an API
function. It is the responsibility of the calling function to preserve the values of A and X prior to the call if
those values are required after the call. This “registers are volatile” policy was selected for efficiency
reasons and has been in force since version 1.0 of PSoC Designer. The C compiler automatically takes
care of this requirement. Assembly language programmers must ensure their code observes the policy,
too. Though some user module API function may leave A and X unchanged, there is no guarantee they
will do so in the future.
For Large Memory Model devices, it is also the caller's responsibility to preserve any value in the
CUR_PP, IDX_PP, MVR_PP, and MVW_PP registers. Even though some of these registers may not be
modified now, there is no guarantee that will remain the case in future releases.
The API routines allow programmatic control of the TX8SW User Module. The following tables list the low
level and high level TX8SW supplied API functions.
Table 5.
Low Level TX8SW API
Function
Description
void TX8SW_Start(void)
Enables user module.
void TX8SW_Stop(void)
Stops user module.
void TX8SW_SendData(BYTE bTxData)
Sends one byte bTxData via TX pin.
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8-Bit Software Serial Transmitter
Table 6.
High Level TX8SW API
Function
Description
void TX8SW_PutString(BYTE * szStr)
Sends RAM located string szStr out through TX pin.
void TX8SW_CPutString(const BYTE * azStr)
Sends ROM located string azStr out through TX pin.
void TX8SW_PutChar(BYTE bData)
Sends one byte via TX pin.
void TX8SW_Write(BYTE * aStr, BYTE bCnt)
Sends RAM located data pointed by aStr with bCnt length.
void TX8SW_CWrite(const BYTE * aStr, INT
iCnt)
Sends ROM located data pointed by aStr with iCnt length.
void TX8SW_PutSHexByte(BYTE bValue)
Sends a bValue BYTE in Hex representation (two characters) via
TX pin.
void TX8SW_PutSHexInt(INT iValue)
Sends a iValue INT in Hex representation (four characters) via
TX pin.
void TX8SW_PutCRLF(void)
Sends a CR and LF characters.
TX8SW_Start
Description:
Enables the TX8SW module, sets the output pin to strong mode and high (serial inactive) state.
C Prototype:
void
TX8SW_Start(void)
Assembly:
lcall
TX8SW_Start
Parameters:
None
Return Value:
None
Side Effects:
See Note ** at the beginning of the API section.
TX8SW_Stop
Description:
Stops the TX8SW module, sets the output pin to high impedance (hi-z analog) mode.
C Prototype:
void
TX8SW_Stop(void)
Assembly:
lcall
TX8SW_Stop
Parameters:
None
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8-Bit Software Serial Transmitter
Return Value:
None
Side Effects:
See Note ** at the beginning of the API section.
TX8SW_SendData
Description:
Sends one byte bTxData via the TX pin.
C Prototype:
void
TX8SW_SendData(BYTE bTxData)
Assembly:
mov
A, bTxData
lcall TX8SW_SendData
Parameters:
bTxData: data to be sent, passed in the Accumulator.
Return Value:
None
Side Effects:
This function does not return until the byte is transmitted.
See Note ** at the beginning of the API section.
TX8SW_PutString
Description:
Sends a RAM located null terminated string, szRamString, out through the TX pin.
C Prototype:
void TX8SW_PutString(BYTE * szRamString)
Assembler:
mov
A, >szRamString
mov
X, <szRamString
lcall TX8SW_PutString
;
;
;
;
Load MSB part of pointer to RAM based null
terminated string.
Load LSB part of pointer to RAM based null
terminated string.
; Call function to send string out TX8SW port
Parameters:
BYTE * szRamString: A pointer to the string to be sent to the TX8SW pin. The MSB is passed in the
Accumulator and the LSB is passed in the X register.
Return Value:
None
Side Effects:
This function does not return until the last character is sent out.
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8-Bit Software Serial Transmitter
See Note ** at the beginning of the API section. Currently, only the IDX_PP page pointer register is
modified.
TX8SW_CPutString
Description:
Sends a constant (ROM), null terminated string out the TX port.
C Prototype:
void TX8SW_CPutString(const BYTE * szRomString)
Assembler:
mov
A, >szRomString
;
;
;
;
Load MSB part of pointer to ROM based null
terminated string.
mov X, <szRomString
Load LSB part of pointer to ROM based null
terminated string.
lcall TX8SW_CPutString ; Call function to send constant string out
; TX8SW port
Parameters:
const BYTE * szRomString: A pointer to a string to be sent to the TX8SW pin. The MSB of the string
pointer is passed in the Accumulator and the LSB of the pointer is passed in the X register.
Return Value:
None
Side Effects:
This function does not return until the last character is sent out.
See Note ** at the beginning of the API section.
TX8SW_PutChar
Description:
Sends one byte via the TX pin.
C Prototype:
void TX8SW_PutChar(BYTE cData)
Assembler:
mov A, cData
lcall TX8SW_PutChar
; Load ASCII character in A
; Call function to send single character to
; TX8SW port.
Parameters:
BYTE cData: The character to be sent to the TX8SW pin. The data is passed in the Accumulator.
Return Value:
None
Side Effects:
This function does not return until the data is sent out.
See Note ** at the beginning of the API section.
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8-Bit Software Serial Transmitter
TX8SW_Write
Description:
Sends RAM located data pointed to by sRamData with bCount length.
C Prototype:
void TX8SW_Write(BYTE * sRamData, BYTE bCount)
Assembler:
mov
push
mov
push
mov
push
lcall
add
A, bCount
A
A, >sRamData
A
A, <sRamData
A
TX8SW_Write
SP, 253
; Load string/array count
; Load MSB part of pointer to RAM string
; Load LSB part of pointer to RAM string
; Make call to function
; Reset stack pointer to original position
Parameters:
BYTE * szRomString: Pointer to the buffer to be sent to the TX8SW pin. BYTE bCount: Number of
bytes to be sent to the TX8SW pin.
Return Value:
None
Side Effects:
This function does not return until the last byte is sent out.
See Note ** at the beginning of the API section. Currently, only the IDX_PP page pointer register is
modified.
TX8SW_CWrite
Description:
Sends ROM located data pointed to by sRomData with iCount length.
C Prototype:
void TX8SW_CWrite(const BYTE * sRomData, INT iCount)
Assembler:
mov
push
mov
push
mov
push
mov
push
lcall
add
A, >iCount
A
A, <iCount
A
A, >sRomData
A
A, <sRomData
A
TX8SW_CWrite
SP, 252
; Load MSB of count
; Load LSB of count
; Load MSB part of pointer to ROM string
; Load LSB part of pointer to ROM string
; Make call to function
; Reset stack pointer to original position
Parameters:
BYTE * szRomData: A pointer to the buffer to be sent to the TX8SW pin.
int iCount: Number of bytes to be sent to the TX8SW pin.
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8-Bit Software Serial Transmitter
Return Value:
None
Side Effects:
This function does not return until the last character is sent out.
See Note ** at the beginning of the API section.
TX8SW_PutSHexByte
Description:
Sends a byte in Hex representation (two characters) via TX8SW pin.
C Prototype:
void TX8SW_PutSHexByte(BYTE bData)
Assembler:
mov A, bData
lcall TX8SW_PutSHexByte
; Load data to be sent to TX8SW
; Call function
Parameters:
BYTE bData: The byte to be converted to an ASCII string.
Return Value:
None
Side Effects:
This function does not return until both characters are sent out.
See Note ** at the beginning of the API section.
TX8SW_PutSHexInt
Description:
Sends an integer value in Hex representation (four characters) via the TX8SW pin.
C Prototype:
void TX8SW_PutSHexInt(INT iData)
Assembler:
mov A, <iData
mov X, >iData
lcall TX8SW_PutSHexInt
; Load LSB in A
; Load MSB in X
; Function call
Parameters:
int iData: Integer to be converted to ASCII string and sent via TX8SW pin.
Return Value:
None
Side Effects:
This function does not return until all four characters are sent out.
See Note ** at the beginning of the API section.
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8-Bit Software Serial Transmitter
TX8SW_PutCRLF
Description:
This function sends a carriage return (0x0D) and a line feed (0x0A) character out the TX8SW port.
C Prototype:
void TX8SW_PutCRLF(void)
Assembler:
lcall TX8SW_PutCRLF
; Send a carriage return and line feed out TX8SW pin
Parameters:
None
Return Value:
None
Side Effects:
This function does not return until the two characters are sent out.
See Note ** at the begining of the API section.
Sample Firmware Source Code
The following is an example of a function that transmits a constant zero-terminated string using the
TX8SW User Module. The code sample in assembly language is:
include "m8c.inc"
include "memory.inc"
include "PSoCAPI.inc"
; part specific constants and macros
; Constants & macros for1 SMM/LMM and Compiler
; PSoC API definitions for all User Modules
export _main
_main:
.LITERAL
MyString: ASCIZ "Sending_Message"
.ENDLITERAL
;TX8SW module enabling
call TX8SW_Start
;Put null-termined string through TX pin
mov A, >MyString
mov X, <MyString
call TX8SW_CPutString
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8-Bit Software Serial Transmitter
Here is the same code written in C:
#include <m8c.h>
#include "PSoCAPI.h"
// part specific constants and macros
// PSoC API definitions for all User Modules
void main(void)
{
TX8SW_Start();
TX8SW_CPutString("Sending_Message\0");
}
Version History
Version
1.2
Originator
DHA
Description
1. Modified Wizard to prevent used pin selection
2. Modified Start API to improve memory management.
1.2.b
Note
DHA
Added CYRF89x35 device support.
PSoC Designer 5.1 introduces a Version History in all user module datasheets. This section documents high level descriptions of the differences between the current and previous user module versions.
Document Number: 001-16838 Rev. *L
Revised May 30, 2013
Page 11 of 11
Copyright © 2008-2013 Cypress Semiconductor Corporation. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility
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assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in life-support systems
where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress' product in a life-support systems application implies that the manufacturer
assumes all risk of such use and in doing so indemnifies Cypress against all charges.
Use may be limited by and subject to the applicable Cypress software license agreement.