From 8ec97abe6ef518a367a16d28c5cec150023691fa Mon Sep 17 00:00:00 2001
From: Roberto Hexsel <roberto@inf.ufpr.br>
Date: Tue, 18 Apr 2017 09:32:09 -0300
Subject: [PATCH] several fixes: remote now reads 1st line of serial.inp;
UART.status.RX flags updated on a DATA-read, UART.status.TX updated on a
status-read; improvements to UART interrupt handler
---
cMIPS/include/handlers.s | 49 ++++++++------
cMIPS/include/start.s | 3 +-
cMIPS/tests/nullifies.expected | 7 +-
cMIPS/tests/nullifies.s | 117 +++++++++++++++++++++++++++++----
cMIPS/tests/uart_defs.c | 2 +
cMIPS/tests/uart_irx.c | 26 +++++---
cMIPS/tests/uart_irx.expected | 1 +
cMIPS/tests/uartrx.c | 9 ++-
cMIPS/tests/uartrx.expected | 1 +
cMIPS/tests/uarttx.c | 7 +-
cMIPS/tests/uarttx.expected | Bin 50 -> 46 bytes
cMIPS/vhdl/uart.vhd | 64 +++++++++---------
12 files changed, 203 insertions(+), 83 deletions(-)
diff --git a/cMIPS/include/handlers.s b/cMIPS/include/handlers.s
index 48121cf..f6e4f31 100644
--- a/cMIPS/include/handlers.s
+++ b/cMIPS/include/handlers.s
@@ -57,9 +57,6 @@ extCounter:
# lw $a1, 1*4($k1)
#----------------------------------
- mfc0 $k0, c0_status # Read STATUS register
- ori $k0, $k0, M_StatusIEn # but do not modify its contents
- mtc0 $k0, c0_status # except for re-enabling interrupts
eret # Return from interrupt
.end extCounter
#----------------------------------------------------------------
@@ -72,6 +69,15 @@ extCounter:
.bss
.align 2
.global Ud
+
+ .equ RXHD,0
+ .equ RXTL,4
+ .equ RX_Q,8
+ .equ TXHD,24
+ .equ TXTL,28
+ .equ TXQ,32
+ .equ NRX,48
+ .equ NTX,52
Ud:
rx_hd: .space 4 # reception queue head index
rx_tl: .space 4 # tail index
@@ -83,18 +89,34 @@ nrx: .space 4 # characters in RX_queue
ntx: .space 4 # spaces left in TX_queue
_uart_buff: .space 16*4 # up to 16 registers to be saved here
- # _uart_buff[0]=UARTstatus, [1]=UARTcontrol, [2]=data_inp, [3]=new,
+ # _uart_buff[0]=UARTstatus, [1]=UARTcontrol, [2]=$v0, [3]=$v1,
# [4]=$ra, [5]=$a0, [6]=$a1, [7]=$a2, [8]=$a3
.set UART_rx_irq,0x08
.set UART_tx_irq,0x10
+ .equ UCTRL,0 # UART registers
+ .equ USTAT,0
+ .equ UDATA,4
+
.text
.set noreorder
.global UARTinterr
.ent UARTinterr
UARTinterr:
+
+ #----------------------------------------------------------------
+ # While you are developing the complete handler, uncomment the
+ # line below
+ #
+ # .include "../tests/handlerUART.s"
+ #
+ # Your new handler should be self-contained and do the
+ # return-from-exception. To do that, copy the lines below up
+ # to, but excluding, ".end UARTinterr", to yours handlerUART.s.
+ #----------------------------------------------------------------
+
lui $k0, %hi(_uart_buff) # get buffer's address
ori $k0, $k0, %lo(_uart_buff)
@@ -105,23 +127,17 @@ UARTinterr:
lui $a0, %hi(HW_uart_addr)# get device's address
ori $a0, $a0, %lo(HW_uart_addr)
- lw $k1, 0($a0) # Read status, remove interrupt request
+ lw $k1, USTAT($a0) # Read status, remove interrupt request
sw $k1, 0*4($k0) # and save UART status to memory
- #----------------------------------
- # while you are developing the complete handler,
- # uncomment the line below and comment out lines up to UARTret
- # .include "../tests/handlerUART.s"
- #----------------------------------
-
andi $a1, $k1, UART_rx_irq # Is this reception?
beq $a1, $zero, UARTret # no, ignore it and return
nop
# handle reception
- lw $a1, 4($a0) # Read data from device
+ lw $a1, UDATA($a0) # Read data from device
- lui $a2, %hi(Ud) # get address for data & flag
+ lui $a2, %hi(Ud) # get address for data & flag
ori $a2, $a2, %lo(Ud)
sw $a1, 0*4($a2) # and return from interrupt
@@ -133,9 +149,6 @@ UARTret:
lw $a1, 6*4($k0) # restore registers $a0,$a1, others?
lw $a0, 5*4($k0)
- mfc0 $k0, c0_status # Read STATUS register
- ori $k0, $k0, M_StatusIEn # but do not modify its contents
- mtc0 $k0, c0_status # except for re-enabling interrupts
eret # Return from interrupt
.end UARTinterr
#----------------------------------------------------------------
@@ -153,10 +166,6 @@ countCompare:
addiu $k1,$k1,num_cycles # set next interrupt in so many ticks
mtc0 $k1,c0_compare # write to COMPARE to clear IRQ
- mfc0 $k0, c0_status # Read STATUS register
- ori $k0, $k0, M_StatusIEn # but do not modify its contents
- mtc0 $k0, c0_status # except for re-enabling interrupts
- ehb
eret # Return from interrupt
.end countCompare
#----------------------------------------------------------------
diff --git a/cMIPS/include/start.s b/cMIPS/include/start.s
index d324172..52875b1 100644
--- a/cMIPS/include/start.s
+++ b/cMIPS/include/start.s
@@ -321,7 +321,7 @@ _excp_0200:
nop
- ## the code for each handler must repeat the exception return
+ ## the code for each handler must contain an exception return
## sequence shown below in excp_0200ret.
handlers_tbl:
j dismiss # no request: 000
@@ -354,7 +354,6 @@ _excp_0200ret:
mtc0 $k0, c0_status # else keep as it was on int entry
ehb
eret # Return from interrupt
- nop
.end _excp_0200
#----------------------------------------------------------------
diff --git a/cMIPS/tests/nullifies.expected b/cMIPS/tests/nullifies.expected
index 9bcd9b0..de0e14a 100644
--- a/cMIPS/tests/nullifies.expected
+++ b/cMIPS/tests/nullifies.expected
@@ -1,3 +1,6 @@
-00000540
-08802000
+
00000000
+ok
+
+ok
+
diff --git a/cMIPS/tests/nullifies.s b/cMIPS/tests/nullifies.s
index dc4b961..7e89f05 100644
--- a/cMIPS/tests/nullifies.s
+++ b/cMIPS/tests/nullifies.s
@@ -22,6 +22,7 @@
.equ numCy,0xc0000000 # enable counter
.equ PRINT,$15
+ .equ STDOUT,$17
.equ COUNT,$16
.equ NL,$13
@@ -84,21 +85,21 @@ _excp_180:
# interrupt handler ------------------------------------------------
#
##
- ## stop the counter, print EPC and CAUSE, and return
+ ## stop the counter, print EPC, and return
##
.org x_EXCEPTION_0200,0
_excp_200:
- sw $zero, 0(COUNT) # stop the counter
+ lw $k0, 0(COUNT) # read the counter and disable counting
+ la $k1, 0x3ffffff
+ and $k0, $k1, $k0
+ sw $k0, 0(COUNT) # stop the counter
- mfc0 $k1, c0_epc # read EPC
- sw $k1, 0(PRINT)
- addi $k1, $k1, 4 # skip interrupted instruction
- nop
- mtc0 $k1, c0_epc # write new EPC
-
- mfc0 $k1, c0_cause # read CAUSE
- sw $k1, 0(PRINT)
+ mfc0 $k1, c0_epc # read EPC -- this is a "return value", keep it!
+ # sw $k1, 0(PRINT)
+ addi $k0, $k1, 4 # skip interrupted instruction
nop
+ mtc0 $k0, c0_epc # write new EPC
+ ehb
eret
#
@@ -122,10 +123,11 @@ _excp_BFC0:
##
.org x_ENTRY_POINT,0
main: la PRINT, x_IO_BASE_ADDR
+ la STDOUT, (x_IO_BASE_ADDR + 1 * x_IO_ADDR_RANGE)
la COUNT, HW_counter_addr
li NL, '\n'
-
+ sw NL, 0(STDOUT) # print a new line
##
## counter will interrupt right on the MULT instruction
## MULT is cancelled by the interrupt
@@ -145,15 +147,106 @@ main: la PRINT, x_IO_BASE_ADDR
nop # counter starts counting
nop
nop
- mult $20, $21 # interrupts on the 4th cycle
+_mult: mult $20, $21 # interrupts on the 4th cycle
# this MULT is cancelled by the handler
mflo $22
sw $22, 0(PRINT) # should print zero
+ la $4, _mult
+ nop
+ nop
+ bne $4, $k1, _err1 # error if EPC != _mult
+ nop
+
+ jal ok
+ nop
+
+ nop # clear out the pipeline
+ nop
+ nop
+ nop
+ nop
+
+
+ ##
+ ## counter will interrupt right on the MTC0 instruction
+ ## the MTC0 disables the interrupts
+ ## MTC0 is NOT cancelled by the interrupt
+ ## handler skips the interrupted instruction
+ ## STATUS.IE must be zero and interrupt is cancelled
+ ##
+ li $6, c0_status_reset # RESET, kernel mode, all else disabled
+
+ li $5, (numCy+4) # interrupt in 4+4 cycles
+ sw $5, 0(COUNT) # it takes four cycles to start counting
+ nop # 4 pipestages
+ nop
+ nop
+
+ nop # counter starts counting
+ # change to STATUS must be in EXEC pipestage
+_mtc0: mtc0 $6, c0_status # this MUST NOT be cancelled by the interrupt
+ nop
+ nop
+ lw $7, 0(COUNT) # was the IRQ taken? If so,
+ la $4, (numCy+4) # value in count must be 4 (b31b30=00)
+ nop
+ nop
+ bne $4, $7, _err2 # error if COUNTER != 4
+ nop
+
+ jal ok
+ nop
here: j exit
nop
+
+_err1: # interrupt was on the wrong instruction
+ li $30, 'n'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 'o'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 't'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 'M'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 'U'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 'L'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 'T'
+ sw $30, x_IO_ADDR_RANGE($15)
+ j exit
+ sw NL, x_IO_ADDR_RANGE($15) # print a newline
+
+_err2: # interrupt was on the wrong instruction
+ li $30, 'w'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 'a'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 's'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, ' '
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 'I'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 'R'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 'Q'
+ sw $30, x_IO_ADDR_RANGE($15)
+ j exit
+ sw NL, x_IO_ADDR_RANGE($15) # print a newline
+
+
+ # nothing wrong
+ok: li $30, 'o'
+ sw $30, x_IO_ADDR_RANGE($15)
+ li $30, 'k'
+ sw $30, x_IO_ADDR_RANGE($15)
+ sw $13, x_IO_ADDR_RANGE($15) # print a newline
+ jr $ra
+ sw $13, x_IO_ADDR_RANGE($15) # print a newline
diff --git a/cMIPS/tests/uart_defs.c b/cMIPS/tests/uart_defs.c
index 699e596..249cc4c 100644
--- a/cMIPS/tests/uart_defs.c
+++ b/cMIPS/tests/uart_defs.c
@@ -35,3 +35,5 @@ typedef struct serial {
Tdata d; // address is (int *)(IO_UART_ADDR+1)
} Tserial;
+
+#define EOT 0x04 // End Of Transmission character
diff --git a/cMIPS/tests/uart_irx.c b/cMIPS/tests/uart_irx.c
index a0c00fc..a2b2bc4 100644
--- a/cMIPS/tests/uart_irx.c
+++ b/cMIPS/tests/uart_irx.c
@@ -4,10 +4,15 @@
// Remote unit reads string from serial.inp and sends it over the
// serial line.
//
+// This program makes use of abstraction to synchronize handler and main().
+// handler sets a flag on receiving a new character; main() waits for
+// flag==1, reads char, makes flag=0.
+//
// UARTinterr, in include/handlers.s, reads newly arrived character,
-// sets a flag and puts character in a buffer. main() reads from the
-// buffer and prints it to the simulator's standard output.
-
+// sets a flag and puts character in a buffer.
+// main() waits for flag==1, then reads from the buffer, prints
+// character to the simulator's standard output, makes flag=0.
+//
#include "cMIPS.h"
@@ -36,7 +41,7 @@ int main(void) { // receive a string through the UART serial interface
ctrl.speed = SPEED;
uart->cs.ctl = ctrl; // initizlize UART
- // handler sets flag=bfr[3] to 1 after new character is received;
+ // handler sets flag=[U_FLAg] to 1 after new character is received;
// this program resets the flag on fetching a new character from buffer
bfr[U_FLAG] = 0; // reset flag
@@ -48,13 +53,16 @@ int main(void) { // receive a string through the UART serial interface
uart->cs.ctl = ctrl;
do {
- while ( (c = (char)bfr[U_FLAG]) == 0 ) // check flag in Ud[1]
- {}; // nothing new
+ while ( (c = (char)bfr[U_FLAG]) == 0 ) // check flag in Ud[]
+ delay_cycle(1); // nothing new, wait
c = (char)bfr[U_DATA]; // get new character
bfr[U_FLAG] = 0; // and reset flag
- to_stdout( (int)c ); // and print new char
- } while (c != '\0'); // end of string?
+ if (c != EOT)
+ to_stdout( c ); // and print new char
+ else
+ to_stdout( '\n' ); // and print new-line
+ } while (c != EOT); // end of transmission?
- return c;
+ return c; // so compiler won't optimize away the last loop
}
diff --git a/cMIPS/tests/uart_irx.expected b/cMIPS/tests/uart_irx.expected
index f1de9d7..56f4ada 100644
--- a/cMIPS/tests/uart_irx.expected
+++ b/cMIPS/tests/uart_irx.expected
@@ -1,3 +1,4 @@
+
abcdef
012345
diff --git a/cMIPS/tests/uartrx.c b/cMIPS/tests/uartrx.c
index b8d0b63..a783eff 100644
--- a/cMIPS/tests/uartrx.c
+++ b/cMIPS/tests/uartrx.c
@@ -51,11 +51,14 @@ int main(void) { // receive a string through the UART serial interface
i = i+1;
while ( (state = (int)uart->cs.stat.rxFull) == 0 )
- if (state == 0) cmips_delay(1); // just do something with state
+ delay_cycle(1); // just do something
s[i] = (char)uart->d.rx;
- to_stdout( s[i] );
+ if (s[i] != EOT)
+ to_stdout( s[i] ); // and print new char
+ else
+ to_stdout( '\n' ); // and print new-line
- } while (s[i] != '\0');
+ } while (s[i] != EOT);
return(state);
diff --git a/cMIPS/tests/uartrx.expected b/cMIPS/tests/uartrx.expected
index f1de9d7..56f4ada 100644
--- a/cMIPS/tests/uartrx.expected
+++ b/cMIPS/tests/uartrx.expected
@@ -1,3 +1,4 @@
+
abcdef
012345
diff --git a/cMIPS/tests/uarttx.c b/cMIPS/tests/uarttx.c
index 7aace2b..f3fa173 100644
--- a/cMIPS/tests/uarttx.c
+++ b/cMIPS/tests/uarttx.c
@@ -69,17 +69,16 @@ int main(void) { // send a string through the UART serial interface
i = i+1;
while ( (state = (int)uart->cs.stat.txEmpty) == 0 )
- {}; // if (state == 1) cmips_delay(2); // just do something with state
+ delay_cycle(1); // do something
uart->d.tx = (int)s[i];
} while (s[i] != '\0'); // '\0' is transmitted in previous line
-
// then wait until last char is sent out of the shift-register to return
startCounter(COUNTING, 0);
while ( (val=(readCounter() & 0x3fffffff)) < COUNTING )
- {};
+ delay_cycle(1);
- return val; // so compiler won't optimize away the last loop
+ return val; // so compiler won't optimize away the last loop
}
diff --git a/cMIPS/tests/uarttx.expected b/cMIPS/tests/uarttx.expected
index 55747baac2bce6b6340fa2ffd40bfe2386392a75..553acfcc0dc12653edd2285e4e73b210c8c80be6 100644
GIT binary patch
delta 5
McmXrgo5-jK00Wu<ApigX
delta 10
RcmdNhV&s~j$IQjR1po+O0YLx&
diff --git a/cMIPS/vhdl/uart.vhd b/cMIPS/vhdl/uart.vhd
index efd0fc2..17cb5de 100644
--- a/cMIPS/vhdl/uart.vhd
+++ b/cMIPS/vhdl/uart.vhd
@@ -26,10 +26,10 @@
-- 001: 1/8 CPU clock rate -- for VHDL/C debugging only
-- 010: 1/16 CPU clock rate -- for VHDL/C debugging only
-- 011: 1/32 CPU clock rate -- for VHDL/C debugging only
--- 100: 230.400 baud
--- 101: 115.200 baud
--- 110: 19.200 baud
--- 111: 9.600 baus
+-- 100: 230.400 bits per second
+-- 101: 115.200 bits per second
+-- 110: 19.200 bits per second
+-- 111: 9.600 bits per second
-- b3=1: signal interrupt on RX buffer full, when a new octet is available
-- b4=1: signal interrupt on TX buffer empty, when TX space is available
-- b5,b6: ignored, not used
@@ -44,7 +44,9 @@
-- b5: receive buffer is full
-- b6: transmit buffer is empty
-- b7: Clear to Send (CTS) is active
--- when CPU reads status register bits 0,1,3,4 are cleared
+--
+-- when CPU reads from RXdat register, bits 0,1,3 are cleared
+-- when CPU reads from STATUS register, bit 4 is cleared
--
-- RX and TX circuits are dobule-buffered
@@ -124,7 +126,7 @@ architecture estrutural of uart_int is
signal rx_ld, rx_shift, rx_next, rx_bfr_full : std_logic;
signal rxdat_1to0, rxdat_new, rxdat_int, rxdat_old : std_logic;
signal rxclk_fall, rxclk_rise, en_rx_clk, rx_done, rxclk : std_logic;
- signal a_overrun, a_framing, sel_delayed, reset_rxck : std_logic;
+ signal a_overrun, a_framing, reset_rxck, s_stat_dly : std_logic;
signal sta_xmit_sto, sta_recv_sto : reg10;
signal err_overrun, err_framing : std_logic;
signal rx_int_set, interr_RX_full, tx_int_set, interr_TX_empty : std_logic;
@@ -150,8 +152,6 @@ begin
interr <= interr_TX_empty or interr_RX_full;
- U_delay: FFDsimple port map (clk, rst, s_stat, sel_delayed);
-
-- TRANSMISSION ===========================================================
-- txreg is updated under the assumption that SW checked TXempty beforehand
U_txreg: register8 port map (clk,rst, s_tx, d_inp(7 downto 0), txreg);
@@ -162,8 +162,10 @@ begin
U_transmit: par_ser10 port map (clk, rst, tx_ld, tx_next,
sta_xmit_sto, txdat);
+ U_STAT_DELAY: FFDsimple port map (clk, rst, s_stat, s_stat_dly);
+
tx_int_set <= ctrl(4) and tx_ld;
- d_int_tx_empty <= (interr_TX_empty or tx_int_set) and not(sel_delayed);
+ d_int_tx_empty <= (interr_TX_empty or tx_int_set) and not(s_stat_dly);
U_tx_int: FFDsimple port map (clk, rst, d_int_tx_empty, interr_TX_empty);
@@ -360,14 +362,14 @@ begin
(sta_recv_sto(9) /= '1' or sta_recv_sto(0)/='0') )
else '0';
- d_err_framing <= (a_framing or err_framing) and not(sel_delayed);
+ d_err_framing <= (a_framing or err_framing) and not(s_rx);
U_framing: FFDsimple port map (clk, rst, d_err_framing, err_framing);
- d_err_overrun <= (a_overrun or err_overrun) and not(sel_delayed);
+ d_err_overrun <= (a_overrun or err_overrun) and not(s_rx);
U_overrun: FFDsimple port map (clk, rst, d_err_overrun, err_overrun);
rx_int_set <= ctrl(3) and rx_done;
- d_rx_int_set <= (rx_int_set or interr_RX_full) and not(sel_delayed);
+ d_rx_int_set <= (rx_int_set or interr_RX_full) and not(s_rx);
U_rx_int: FFDsimple port map (clk, rst, d_rx_int_set, interr_RX_full);
@@ -778,6 +780,7 @@ entity remota is
inpDat : in std_logic; -- serial input
outDat : out std_logic; -- serial output
bit_rt : in reg3); -- selects bit rate
+ constant EOT : reg8 := x"04"; -- end of transmission character
end remota;
architecture behavior of remota is
@@ -836,10 +839,10 @@ begin
tx_dbg_st <= integer(tx_state'pos(tx_current_st)); -- debugging only
- U_tx: process (tx_current_st, start)
+ U_tx: process (tx_current_st, start, rst)
variable sentence : line;
variable char : character;
- variable good, send_null : boolean;
+ variable good, send_eot : boolean;
variable bfr : reg8;
variable j : integer;
begin
@@ -848,13 +851,13 @@ begin
when st_wait => -- 12 wait for starting signal
outDat <= '1';
tx_run <= '0'; -- hold TX clock
- send_null := FALSE;
- if start = '0' then
+ send_eot := FALSE;
+ if start = '0' then
tx_next_st <= st_wait;
else
- if not endfile(input_stream) then
+ if not endfile(input_stream) and rst = '1' then
readline( input_stream, sentence ); -- read first line of text
- -- assert false report "fst line: "&integer'image(sentence'length);
+ assert TRUE report "fst line: "&integer'image(sentence'length);
j := 1;
tx_next_st <= st_init;
else
@@ -869,15 +872,15 @@ begin
if not endfile(input_stream) then
if j > sentence'right then -- read new line of input
readline( input_stream, sentence );
- -- assert false report "new line: "&integer'image(sentence'length);
+ assert TRUE report "new line: "&integer'image(sentence'length);
bfr := x"0a"; -- new line
j := 0;
elsif sentence'length = 0 then
bfr := x"0a"; -- send new line for empty line
- -- assert false report "empty line: " & integer'image(j)&" " & LF;
+ assert TRUE report "empty line: " & integer'image(j)&" " & LF;
else
read (sentence, char, good);
- -- assert false report "read: " & integer'image(j) & " " &char;
+ assert TRUE report "read: " & integer'image(j) & " " &char;
bfr := std_logic_vector(to_signed( character'pos(char), 8));
end if;
tx_next_st <= st_start;
@@ -916,12 +919,12 @@ begin
outDat <= '1';
tx_next_st <= st_idle;
when st_done => -- 13 wait forever
- if send_null = FALSE then
- bfr := x"00"; -- send out a NULL character
- send_null := TRUE;
+ if send_eot = FALSE then
+ bfr := EOT; -- send out an END-OF-TRANSMISSION
+ send_eot := TRUE;
tx_next_st <= st_start;
else
- tx_next_st <= st_done; -- no more input, done!
+ tx_next_st <= st_done; -- no more input, wait forever
outDat <= '1';
end if;
tx_run <= '0'; -- stop clock
@@ -968,11 +971,7 @@ begin
rx_next_st <= st_start;
when st_start =>
reset_rxck <= '0';
- -- if rising_edge(rx_clk) then
rx_next_st <= st_b0;
- -- else
- -- rx_next_st <= st_start;
- -- end if;
when st_b0 =>
if falling_edge(rx_clk) then
recv(0) <= inpDat;
@@ -1039,8 +1038,11 @@ begin
rx_run <= '0';
rx_next_st <= st_idle;
- write ( msg, character'val(to_integer( unsigned(recv))) );
- if recv = x"00" or recv = x"0a" then
+ if ((recv /= x"0a") and (recv /= x"04")) then
+ write ( msg, character'val(to_integer(unsigned(recv))) );
+ end if;
+
+ if ((recv = x"0a") or (recv = x"04")) then
writeline( output_stream, msg );
end if;
--
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